UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS 


COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,  CALIFORNIA 


WALNUT  CULTURE  IN  CALIFORNIA 
WALNUT  BLIGHT 


BY 


RALPH  E.  SMITH 

ASSISTED  BY 

CLAYTON  O.  SMITH  and  HENRY  J.  RAMSEY 


BULLETIN  No.  231 

(BERKELEY,  CALIFORNIA,  AUGUST,  1912) 


Friend  Wm.  Richardson,  Superintendent  of  State  Printing 

sacramento,  california 

1912 


Benjamin  Ide  Wheeler,  President  of  the  University. 

EXPERIMENT  STATION  STAFF. 

E.  J.  Wickson,  M.A.,  Director  and  Horticulturist. 

E.  W.   Hilgard,  Ph.D.,  LL.D.,   Chemist    (Emeritus). 
W.  A.  Setchell,  Ph.D.,  Botanist. 

Leroy  Anderson,  Ph.D.,  Dairy  Industry. 

M.  E.  Jaffa,  M.S.,  Nutrition  Expert. 

R.   H.  Loughridge,  Ph.D.,   Soil  Chemist  and  Physicist    (Emeritus). 

C.  W.  Woodworth,  M.S.,  Entomologist. 

Ralph  E.   Smith,  B.S.,  Plant  Pathologist  and  Superintendent  of  Southern  California 

Pathological  Laboratory  and  Experiment  Station. 
P.  R.  Marshall,  B.S.A.,  Animal  Industry. 
G.  W.  Shaw,  M.A.,  Ph.D.,  Experimental  Agronomist  and  Agricultural  Technologist,  in 

charge  of  Cereal  Stations. 

B.  A.  Etcheverry.  B.S.,  Irrigation  Expert. 

F.  T.   Bioletti,  M.S.,  Viticulturist. 

W.  T.  Clarke,  B.S.,  Assistant  Horticulturist  and  Superintendent  of  University  Exten- 
sion in  Agriculture. 
John  S.  Burd,  B.S.,  Chemist,  in  charge  of  Fertilizer  Control. 
J.  E.  Coit,  Ph.D.,  Pomologist,  Riverside. 

C.  B.  Lipman,  Ph.D.,  Soil  Chemist  and  Bacteriologist. 

George    E.    Colby,    M.S.,    Chemist    (Fruits,    Waters,    and    Insecticides),    in    charge    of 

Chemical  Laboratory. 
H.  J.  Quayle,  M.S.,  Assistant  Entomologist. 
H.  M.  Hall,  Ph.D.,  Assistant  Botanist. 
C.  M.   Haring,  D.V.M.,    Veterinarian  and  Bacteriologist. 
E.  B.  Babcock,  B.S.,  Agricultural  Education. 
W.  B.  Herms,  M.A.,  Assistant  Entomologist. 
W.  T.  Horne,  B.S.,  Assistant  Plant  Pathologist. 
L.  M.   Davis,  B.S.,  Assistant  Dairy  Industry. 
W  W.  Bonns,  M.S.,  Assistant  Pomologist. 

A.  J.  Gaumnitz,  Assistant  Agronomist,  University  Farm,  Davis. 
T.   Francis  Hunt,   B.S.,  Assistant  Plant  Pathologist. 

P.  L.  McCreary,  B.S.,  Chemist  in  Fertilizer  Control. 

E.  H.   Hagemann,  Assistant  in  Dairying,   Davis. 

R.  M.  Roberts,  Farm  Manager,  University  Farm,  Davis. 
J.  I.  Thompson,  B.S.,  Assistant  Animal  Industry,  Davis. 
J.  C.  Bridwell,  B.S.,  Assistant  Entomologist. 
L.  Bonnet,  LA.,  Assistant  Viticulturist. 

F.  C.  H.  Flossfeder,  Assistant  in  Viticulture,  University  Farm,  Davis. 
P.  L.  Hibbard,  B.S.,  Assistant  Fertilizer  Control  Laboratory. 

C.  H.  McCharles,  M.S.,  Assistant  Agricultural  Chemical  Laboratory. 

B.  A.  Madson,  B.S.A.,  Assistant  Experimental  Agronomist. 

Walter  E.  Packard,  M.S.,  Field  Assistant  Imperial  Valley  Investigation,  El  Centre 
S.  S.  Rogers,  B.S.,  Assistant  Plant  Pathologist,  Plant  Disease  Laboratory,  Whittier. 

C.  O.   Smith,  M.S.,  Assistant  Plant  Pathologist,   Plant  Disease  Laboratory,  Whittier. 

E.  H.  Smith,  M.S.,  Assistant  Plant  Pathologist. 

C.  L.  Roadhouse,  D.V.M.,  Assistant  in  Veterinary  Science. 

F.  M.  Hayes,  D.  V.  M.,  Assistant  Veterinarian. 
P.  S.  Burgess,  M.  S.,  Assistant  Soil  Chemist. 
W.   F.   Gericke,  B.S.,  Assistant  Soil  Chemist. 

M.  E.  Stover,  B.S.,  Assistant  in  Agricultural  Chemical  Laboratory. 
W.  H.  Volck,  Field  Assistant  in  Entomology,  Watsonville. 
E.  L.  Morris,  Field  Assistant  in  Entomology,  San  Jose. 

E.  E.  Thomas,  B.S.,  Assistant  Chemist,  Plant  Disease  Laboratory,  Whittier. 
A.   B.   Shaw,  B.S.,  Assistant  in  Entomology. 

G.  P.  Gray,  M.S.,  Chemist  in  Insecticides. 

H.   D.    Young,   B.S.,   Assistant  in  Agricultural   Chemistry,    Plant   Disease   Laboratory, 

Whittier. 
A.  R.  Tylor,  B.S.,  Assistant  in  Plant  Pathology,  Plant  Disease  Laboratory,  Whittier. 
W.  V.  Cruess,  B.  S.,  Assistant  in  Zymology. 
J.  F.  Mitchell,  D.V.M.,  Assistant  in  Veterinary  Laboratory. 
W.  A.  Boys,  B.S.,  Assistant  Cerealist. 
M.  R.  Miller,  B.S.,  Assistant  Chemist  in  Insecticides. 

F.  H.  Wilson,  B.S.,  Assistant  in  Soil  Chemistry. 
W.  M.  Mertz,  Assistant  in  Pomology,  Riverside. 

Anna  M.  Lute,  A.B.,   Scientific  Assistant,  U.  S.  Department  of  Agriculture. 
J.  C.  Roper,  Patron,  University  Forestry  Station,  Chico. 
E.   C.   Miller,  Foreman,   Forestry   Station,   Chico. 

D.  L.  Bunnell,  Secretary  to  Director. 


CONTENTS. 

Page 

INTRODUCTION    119 

SPECIES  OF  WALNUT. 

The   English   Walnut 128 

American  Black  Walnut  (Juglans  nigra) 128 

California  Black  Walnuts 128 

Northern  California  Black  Walnut 129 

Southern  California  Type 138 

Relationship  Between  the  Southern  and  Northern  California  Types  of 

Black   Walnut   141 

Other  Native  Walnuts  of  the  Southwest 146 

Native  Walnuts  of  Arizona 147 

Native  Walnuts  of  Texas 149 

Native  Walnuts  of  New  Mexico 150 

The  Butternut   (Juglans  cinerea) 151 

Foreign  Walnut  Species 152 

Juglans  sieboldiana 152 

Juglans  cordiformis 152 

Juglans  mandshurica 152 

Juglans  boliviensis 152 

Pterocarya  caucasica 152 

Hybrid  Walnuts 152 

Paradox  Hybrids 154 

Seedlings  of  Paradox  Trees 162 

Royal  Hybrid  Walnuts 163 

Seedlings  of  Royal  Trees 167 

Freak  Walnut  Trees 168 

Fossil  Walnut  Species 171 

WALNUT  CULTURE   IN  CALIFORNIA— 171 

History    171 

Location  for  Walnuts 176 

Climate    176 

Frost    176 

Heat 177 

Soil    178 

Distance  of  Planting 179 

Interplanting    179 

Culture   182 

Soil   Handling    182 

Irrigation    183 

Fertilization    185 

Pruning  189 

Crop  Handling   192 

Picking    193 

Washing    193 

Packing-House  Operations  195 

Sampling 195 

Bleaching    196 

Grading   197 

Walnut   Grades   198 

Selling   199 


Contents — Continued. 

Page 
WALNUTS  IN  CALIFORNIA— Continued. 

Propagation  of'the  Walnut 200 

Rootstocks 200 

English  Walnut  Root 202 

Eastern  Black  Root   (Juglans  nigra) 202 

Northern  California  Black  Root   (Juglans  hindsii) 202 

Southern  California  Black  Root  (Juglans  calif ornica) 203 

Hybrid  Roots 204 

Paradox    Hybrid    Roots 205 

Royal  Hybrid  Roots 210 

Planting  the  Nuts  in  Place 211 

^Planting  Black  Walnut  Seedlings  in  Orchard  Form 212 

Raising  the  Trees  in  the  Nursery 214 

Seed  Treatment 214 

Grafting 217 

Time   of   Grafting 218 

The  Scion 219 

Grafting    220 

Budding 225 

Methods   of   Top-Working 230 

Top-Grafting 230 

Top-Working  by   Budding 242 

Digging    245 

Planting 253 

VARIETIES  OF  THE  ENGLISH  WALNUT 254 

Commercial  Varieties 258 

Chase  258 

Concord   263 

Eureka 269 

Franquette    277 

Placentia  (Placentia  Perfection) 283 

Prolific  (Disher's  Prolific,  Ware's  Prolific) 289 

San  Jose  (San  Jose  Mayette,  Wiltz) 295 

Opinion  of  an  Expert  Walnut  Buyer 299 

Size  and  Weight  of  Principal  Walnut  Varieties 300 

MISCELLANEOUS  AND  LESS  PROMINENT  VARIETIES 305 

Acme    305 

Barthera    305 

A.  Bijou   (Gant) 305 

Bishop   307 

Chaberte    307 

Cluster 308 

El  Monte  (El  Monte  Large) 308 

Eureka  No.  2 309 

Ford's  Improved 309 

Ford's  Eureka 309 

Grenoble    309 

Hale 309 

Hicks.     See  Bishop 310 

Hildebrand.     See  Mayette 310 

Kaghazi 310 

Keesling 313 

Klondyke 313 

Laciniated 313 

Lane 313 

Main.    See  Bishop 313 

Mayette  313 


Contents — Continued. 

Page. 
MISCELLANEOUS  AND  LESS  PROMINENT  VARIETIES— Continued. 

Mayette  Blanc 316 

Mayette  Rouge 316 

Mesange 316 

Meylan 316 

Monstreuse    316 

Neff   (Ncfs  Prolific) 316 

Paper  Shell 317 

Parisienne  317 

Persian.     See  Kaghazi 317 

Powell.     See  Mayette 317 

Pride  of  Ventura 317 

Proeparturiens 318 

Santa  Barbara  Soft  Shell 318 

Santa  Rosa 318 

Seedling.     See  Santa  Barbara  Soft  Shell 318 

Serotina 318 

Soft  Shell.     See  Santa  Barbara  Soft  Shell 1 318 

Treyve   318 

Tribble.     See  Mayette 319 

Vourey 319 

Wagner    319 

Willson    (Willson's   Wonder) 319 

DISEASES  AFFECTING  THE  WALNUT 320 

Walnut  Blight  or  Bacteriosis 320 

Host 320 

Popular  Name  of  Disease 321 

Geographical  Distribution 321 

History  of  Disease  in  California 322 

Losses  from  Blight 323 

Earlier  Studies 324 

v   Cause  of  Disease 325 

Confusion  with  Marsonia  juglandis 325 

Characteristics  of  Bacteriosis 328 

On  Branches 328 

Bacteriosis  is  not  Die-Back 329» 

On  Nursery  Trees 329 

Leaves    329 

Catkins 329 

Nuts   329 

Blossom  End  Infection 332 

Lateral  Nut  Infection 333 

Late  Infections 333 

White  Deposit  on  Diseased  Tissue 335 

Winter  Habitat  of  Germ 335 

Secondary  Infection 337 

Effect  of  Climate 337 

Fogs  and  Moisture 338 

Insects  338 

How  the  Germ  Enters  the  Tissue 339 

Two  Seasons  Compared 339 

Non-blighting  of  Late-Blooming  Trees 341 

Immunity 342 

Isolation    342 

A  More  Technical  Study  of  the  Walnut  Organism 343 

Pseudomonas  juglandis  Pierce 343 

Morphology 343 

Cultural  Characteristics _. 344 


Contents — Continued. 

DISEASES  AFFECTING  THE  WALNUT— Continued.  Page 

A  More  Technical  Study  of  the  Walnut  Organism — Continued. 

Artificial  Inoculations 351 

More  Detailed  Account  of  Inoculation  Experiments 355 

Inoculations  on  Other  Species  of  Juglans 357 

Action  of  Germicides  on  Walnut  Organism 361 

Control  of  Walnut  Blight 363 

Spraying    363 

Blight  Control  by  Means  of  Applications  to  the  Soil 367 

Resistant  Varieties 367 

Working  Over  Seedling  Groves  to  Better  Varieties 369 

Die-Back    372 

Sunburn — Back  Sap 373 

Perforation 376 

Crown  Gall 377 

Root  Rot — Oak  Fungus — Toadstool  Disease 378 

Seedling  Root  Rot — Wilt 379 

Little  Leaf — "Yellows" 379 

Shriveled  Meat 382 

Aphis 383 

Aphis  Control 384 

Mixtures  for  Spraying 385 

BLISTER  MITE— ERINOSE 385 

RED  SPIDER 385 

ACKNOWLEDGMENT    398 


WALNUT  CULTURE  IN  CALIFORNIA. 


WALNUT  BLIGHT. 

By  Ralph  E.  Smith. 
Assisted  by  Clayton  O.  Smith  and  Henry  J.  Ramsey. 

The  present  bulletin  represents  the  results  of  the  most  extensive,  and, 
perhaps,  the  most  important  investigation  undertaken  by  the  depart- 
ment of  plant  pathology  since  its  foundation.  When  the  writer  first 
came  to  California  in  1903,  one  of  the  most  conspicuous  and  most  seri- 
ous plant  diseases  then  prevalent  in  the  State  was  the  so-called  walnut 
blight.  The  disease,  while  comparatively  a  new  one  at  that  time,  had 
reached  all  the  important  walnut-growing  districts  and  was  reputed  to 
have  been  the  cause  of  a  diminution  of  at  least  one  half  in  the  walnut 
crop  of  the  State.  The  trouble  had  been  under  investigation  for  some 
little  time  by  Professor  Newton  B.  Pierce,  then  of  the  United  States 
Department  of  Agriculture,  who  had  succeeded  in  definitely  establish- 
ing its  cause  and  had  undertaken  considerable  work  along  the  line  of 
treatment  for  its  suppression,  and  also  that  of  developing  varieties  of 
the  walnut  which  might  be  immune  to  this  disease.  Professor  Pierce, 
however,  was  burdened  with  much  other  work,  which  prevented  his  giv- 
ing to  walnut  blight  the  amount  of  attention  which  the  walnut  grow- 
ers felt  that  the  subject  justified ;  indeed,  the  importance  of  the  matter, 
owing  to  the  extensive  ravages  of  the  disease,  seemed  to  justify  every 
possible  effort  toward  finding  means  for  reducing  the  great  losses 
occasioned  by  this  trouble.  The  walnut  growers'  associations  had, 
therefore,  offered  a  standing  reward  of  twenty  thousand  dollars  for 
a  feasible  remedy  for  the  blight,  and  were  eager  to  demand  all  possible 
assistance  in  solving  this  problem.  The  legislature  of  1905  made  an 
appropriation  of  four  thousand  dollars  to  the  Regents  of  the  University 
of  California,  directing  them  to  cause  to  be  prosecuted  investigations 
looking  for  a  remedy  for  the  walnut  blight,  and  under  this  appropria- 
tion the  present  work  was  started. 

In  the  spring  of  1905  a  laboratory  was  established  in  the  city  of 
Whittier,  Los  Angeles  County,  primarily  for  the  study  of  walnut 
blight.  This  laboratory  was  placed  in  charge  of  Mr.  Albert  M.  West, 
an  experienced  bacteriologist,  who,  under  the  direction  of  the  writer, 
commenced  the  investigations  which  are  reported  in  this  bulletin.  The 
work  was  largely  contributed  to  in  later  years  by  Messrs.  Clayton  0. 
Smith  and  Henry  J.  Eamsey,  the  latter  working  particularly  upon  the 
pomological  side  of  the  investigation,  while  Mr.  Smith's  work  has  been 


120  UNIVERSITY   OF    CALIFORNIA EXPERIMENT   STATION. 

largely  confined  to  the  study  of  the  bacterial  organism  which  is  the  cause 
of  the  disease. 

It  was  found  early  in  the  work  that  the  problem  was  much  broader 
than  one  simply  of  bacteriology  or  plant  pathology  proper,  and  as  the 
investigation  developed,  it  became  necessary  to  study  the  whole  sub- 
ject of  walnut  culture  from  a  horticultural  or  pomological  standpoint. 
The  establishment  of  the  Southern  California  Plant  Disease  Laboratory 
at  Whittier  as  a  permanent  institution  made  such  work  possible.  Soon 
after  the  location  of  this  laboratory,  space  was  obtained  on  the  grounds 
of  the  Whittier  State  School  for  orchard  planting  of  walnuts.  Upon 
this  ground  there  was  commenced,  in  the  spring  of  1907,  an  experi- 
mental walnut  orchard,  in  which  may  now  be  seen  representative  trees 
of  all  the  important  varieties.  Upon  the  same  grounds,  and  also  those 
of  the  laboratory  proper,  a  large  amount  of  nursery  work  was  also 
commenced  in  connection  with  the  study  of  methods  of  propagation 
of  the  walnut,  testing  of  different  roots  and  other  similar  subjects. 
In  1909  this  portion  of  the  work  was  mostly  transferred  to  the  Pasa- 
dena City  Farm  near  Alhambra,  where  it  could  be  carried  out  on  a 
much  larger  scale.  In  addition  to  nursery  experiments,  considerable 
work  has  also  been  done  in  the  vicinity  of  Whittier  and  in  other  places 
in  top-grafting  walnut  trees  in  the  orchard  with  the  idea  of  determin- 
ing the  feasibility  of  working  over  undesirable  trees  to  better  varieties. 
Much  work  has  been  done  in  searching  for  desirable  walnut  trees  all 
over  the  State,  and  such  trees  when  found  have  been  tested  out  quite 
extensively  by  propagation,  both  in  the  nursery  and  upon  old  trees,  as 
mentioned  above.  A  large  amount  of  top-working  of  this  sort  has  been 
done  upon  the  Pasadena  City  Farm,  where  a  large  seedling  walnut 
orchard  already  existed,  and  also  in  conjunction  with  several  growers 
in  various  parts  of  the  State.  Scions  and  nursery  trees  of  promising 
varieties  have  also  been  distributed  quite  extensively  during  the  past 
three  or  four  years.  In  this  way  many  new  varieties  will  be  tested  in 
various  parts  of  the  State  much  more  quickly  than  would  otherwise 
have  been  the  case.  Considerable  testing  of  root  stocks  has  also  been 
brought  about  by  the  same  means.  A  line  of  work  similar  to  that  at 
Whittier  has  also  been  inaugurated  on  the  University  Farm  at  Davis, 
and  it  is  hoped  that  this  work  may  be  continued  and  extended  there 
on  account  of  the  growing  importance  of  the  walnut  industry  in  the 
northern  part  of  the  State.  As  now  presented,  the  results  of  this  inves- 
tigation cover  practically  all  phases  of  the  subject  of  walnut  culture  in 
California,  both  north  and  south. 

The  English  or  Persian  walnut,  Juglans  regia,  constitutes  one  of  the 
most  important  and  one  of  the  most  attractive  tree  crops  of  California. 
In  southern  California,  to  which  portion  of  the  State  the  crop  on  a 


Bulletin   231]  WALNUT   CULTURE   IN   CALIFORNIA.  121 

commercial  basis  has  thus  far  been  largely  confined,  the  walnut  is  sec- 
ond only  to  the  orange  in  prominence.  Under  favorable  and  normal 
conditions  walnut  growing  is  one  of  the  most  attractive  horticultural 
pursuits  which  can  be  imagined.  The  trees  require  comparatively  little 
care  compared  with  citrus  fruits,  and  they  are  subject  to  comparatively 
few  pests  or  diseases.  The  price  of  the  crop  has  been  almost  invariably 
good,  and  first-class  walnuts  have  always  sold  readily  at  excellent  prices. 
The  product  is  not  subject  to  decay,  freezing,  or  other  dangers  which 
are  common  to  most  fruit  crops.  No  unusual  skill  is  required  to  con- 
duct a  well-established  walnut  grove,  and  all  in  all  this  crop  is,  as  said 
above,  perhaps  the  most  attractive  and  the  best  adapted  to  the  average 
settler  coming  to  California  when  favorable  conditions  for  its  produc- 
tion obtain. 

Unfortunately,  this  bright  picture  of  the  walnut  industry  has  been 
seriously  marred  during  recent  years  by  the  disease  above  referred 
to,  and  various  evils  which  have  been  more  or  less  attendant  upon  it. 
Fortunately,  however,  the  prospects  of  the  industry  are  at  present  very 
much  brighter  than  they  have  been  in  the  recent  past,  and  there  is  now 
every  reason  to  believe  that  walnut  growing  is  again  coming  into  its 
own  upon  a  new  and  better  basis,  as  one  of  our  best  horticultural  pur- 
suits. The  walnut  has  been  grown  in  California  to  a  greater  or  less 
extent  since  the  early  days  of  white  settlement,  but  it  is  only  within 
about  the  last  twenty-five  years  that  the  crop  has  assumed  the  rank  of 
an  important  horticultural  product.  Up  to  about  1900  the  production 
of  walnuts  in  the  State  rapidly  increased,  reaching  an  amount  in  that 
year  which  was  not  exceeded  until  1911,  and  which  fell  off  nearly  one 
half  during  the  intervening  period.  Until  very  recently  about  the 
whole  commercial  crop  was  produced  in  southern  California,  and  almost 
exclusively  in  the  counties  of  Santa  Barbara,  Ventura,  Los  Angeles, 
and  Orange.  In  these  counties,  which  still  contain  by  far  the  bulk  of 
our  walnut  acreage,  there  is  probably  at  present  more  than  thirty 
thousand  acres  of  walnuts,  young  and  old.  It  was  thought  at  first  that 
this  portion  of  the  State  was  the  only  one  adapted  to  this  crop,  but 
later  experience  has  shown  this  idea  to  be  erroneous ;  and  especially 
since  land  values  have  become  so  high  in  much  of  the  southern  Cali- 
fornia walnut  country,  and  the  citrus  industry  has  extended  over  much 
of  the  available  walnut  land  of  that  portion  of  the  State,  the  walnut 
has  commenced  to  go  north,  so  that  at  present  there  is  a  strong  indica- 
tion that  large  walnut  districts  in  the  future  may  be  found  in  the  cen- 
tral portion,  probably  within  a  radius  of  one  hundred  and  fifty  miles 
from  San  Francisco,  as  well  as  in  the  southern  districts. 


122  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


Fig.  1. — Bloom  of  English  walnut,  showing  catkins  (A)  coming  from  the  old  wood, 
and  the  new  growth  and  leaves  with  two  young  nuts  or  pistillate  blooms  (B)  at 
the  end. 


Bulletin    231]  WALNUT    CULTURE   IN   CALIFORNIA.  123 

THE  ENGLISH  WALNUT. 

(Juglans    regia.) 

"Juglans  regia,  which  is  a  large  and  lofty  tree  with  stout,  spread- 
ing branches,  is  probably  indigenous  to  the  mountains  of  Greece,  in 
Armenia,  in  the  region  south  of  the  Caucasus  and  the  Caspian  Sea,  on 
the  northwestern  and  northern  Himalayas,  and  in  Burmah  (A.  de  Can- 
dolle,  Origine  des  Plantes  Cultivees,  342).  It  was  cultivated  in  north- 
ern India  in  very  early  times,  and  carried  then  to  China,  where  it  is 
still  grown  on  a  large  scale  (Bretschneider,  On  the  Value  and  Study 
of  Chinese  Botanical  Works,  16;  Early  European  Researches  into  the 
Flora  of  China,  174) .  It  is  probably  not  indigenous,  however,  to  China, 
nor  is  there  any  evidence  that  this  tree  is  a  native  of  Japan,  as  many 
authors  have  believed,  although  it  is  occasionally  seen  in  that  country 
in  the  neighborhood  of  human  habitations.  The  Greeks  cultivated  a 
variety  of  this  tree  obtained  from  Persia;  the  Romans  carried  it  to 
Italy,  whence  its  cultivation  as  a  fruit  tree  has  spread  through  all  the 
countries  of  southern  and  western  Europe,  the  Pacific  states  of  North 
America,  Chile,  and  other  temperate  regions.  The  nut  of  the  wild  tree 
is  small,  with  a  thick,  hard  shell  and  small  kernel,  and  is  scarcely 
edible.  "• 

The  walnut  tree  is  naturally  of  rapid  and  thrifty  growth,  and  forms 
an  attractive,  decidedly  ornamental  tree,  with  a  clean  trunk  and  tall, 
spreading  top.  The  bark  of  the  young  growth  is  usually  of  a  dark 
green  color  with  a  smooth,  glossy  appearance,  that  of  the  larger  limbs 
light  colored  or  nearly  white  and  fairly  smooth,  with  a  trunk  of  the 
same  appearance,  the  bark  remaining  smooth  until  the  tree  becomes 
of  considerable  age  and  size.  The  fruit  is  a  true  nut,  being  borne  in 
an  outer,  fibrous,  rather  fleshy  enveloping  husk  or  shuck,  which  opens 
and  allows  the  nut  to  drop  out  freely  when  matured.  The  walnut  in 
its  best  commercial  form  is  one  of  the  best  of  nuts,  being  of  good  size, 
attractive  appearance,  easily  cracked,  and  having  a  kernel  of  pleasing 
flavor  and  attractive  appearance,  which  is  readily  removed  from  the 
shell.    It  is  also  healthful  and  nutritious  and  a  valuable  article  of  food. 

The  foliage  of  the  tree  is  composed  of  large,  compound,  pinnate 
leaves,  which  are  deciduous  in  the  fall.  The  flowers  are  of  two  kinds, 
staminate  and  pistillate  (male  and  female),  both  born  on  the  same  tree. 
The  staminate  blossoms  are  born  on  long,  pendulous  catkins,  which 
develop  in  spring  from  naked  buds  already  formed  on  the  twigs  of 
the  preceding  year.  These  catkins  contain  an  abundance  of  light,  dusty, 
yellow  pollen,  which  is  carried  by  the  wind  to  the  pistillate  or  fruiting 


♦Sargent,   Silva  of  North  America. 


12-4  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

blossoms.  The  latter  are  produced  at  the  tips  of  young  shoots  coming 
out  in  the  spring  from  terminal  buds  on  twigs  of  the  previous  year's 
growth.     These  consist  of  miniature  nuts,  or  ovaries,  each  bearing  at  its 


Fig.   2. — Mature  walnuts,   dropping  from  shucks.      (Courtesy  Kruckeberg  Press.) 

extremity  a  two-branched,  feathery  stigma,  which  is  designed  to  catch 
the  pollen  coming  in  the  air  from  the  catkins.  After  pollination  the 
stigmas  wither  away  and  the  pistillate  flowers  develop  into  nuts.     In 


Bulletin    231]  WALNUT    CULTURE   IN   CALIFORNIA.  125 

California  most  of  the  blooming  takes  place  in  April  and  May,  although 
some  unusually  early  or  late  trees  bloom  previous  to  or  later  than  this 
period.     The  nuts  commonly  mature  during  September  and  October. 

The  English  walnut  grows  readily  from  seed,  if  the  nuts  are  not 
allowed  to  become  too  dry,  and  are  planted  with  plenty  of  moisture  dur- 
ing the  spring  following  their  production.  The  seedlings  are  of  strong 
and  vigorous  growth,  but  in  this  species  do  not  usually  make  very  much 
growth  in  height  during  the  first  season.  A  large  taproot  is  formed, 
usually  longer  and  thicker  than  the  stem  above  ground.  The  latter 
remains  comparatively  short  during  the  first  year,  but  makes  very  much 
more  growth  the  second  year.  Trees  averaging  only  about  one  foot  in 
height  at  the  end  of  the  first  year  will  frequently  make  a  growth  of 
ten  or  twelve  feet,  or  even  more,  the  second  year.  Seedling  trees, 
though  varying  widely,  are  usually  vigorous,  thrifty  and  long-lived, 
so  long  as  soil  and  climatic  conditions  are  favorable.  The  English 
walnut  on  its  own  root,  however,  has  little  adaptability  to  unfavorable 
conditions,  and  is  very  easily  injured  or  killed  by  lack  of  moisture, 
excessive  moisture,  poor  soil,  or  other  unfavorable  conditions.  While  a 
long-lived  tree  in  the  Old  World,  growing  in  regions  of  abundant  nat- 
ural rainfall,  the  seedling  walnut  has  proven  itself  much  shorter-lived  in 
California,  and  many  of  the  older  groves  have  largely  died  out.  There 
are  a  few  trees  in  the  State  close  to  sixty  years  of  age,  but  these  are 
mostly  in  the  northern  part,  where  the  rainfall  is  fairly  abundant.  In 
the  south  many  trees  and  groves  planted  less  than  forty  years  ago  have 
almost  entirely  died  out,  largely  on  account  of  an  uncertain  or  irregu- 
lar supply  of  soil  moisture.1 

The  seedling  English  walnut  is  rather  slow  in  coming  into  bearing, 
most  trees  producing  very  few  nuts  until  the  fifth  or  sixth  year  after 
planting  or  even  later.  Different  trees,  however,  vary  widely  in  this 
respect.  The  production  per  tree  also  varies  greatly.  The  average 
product  per  year  for  the  older  seedling  groves  of  the  State  is  scarcely 
more  than  50  pounds  per  tree,  although  many  individual  trees  far 
exceed  this.  One  hundred  pounds  per  tree  at  an  age  of  fifteen  to 
twenty  years  may  be  considered  quite  satisfactory,  according  to  pres- 
ent production,  while  some  individual  trees  of  particularly  large  size 
and  heavy  bearing  qualities,  run  up  to  300  pounds  or  a  little  more. 
There  are  a  few  very  large  old  seedling  trees  in  the  State,  standing  in 
good  soil  with  no  other  trees  close  about  them,  which  have  produced  as 
high  as  400  or  even  500  pounds  of  nuts  per  year,  but  this  is  very  excep- 
tional and  cannot  be  considered  on  the  same  basis  with  trees  planted  in 

belong  (Rep.  Cal.  Bd.  Hort.  1895-96)  quotes  accounts  of  Old  World  walnut  trees 
of  ten,  fifteen  or  even  more  feet  in  diameter  and  bearing  as  much  as  2,000  pounds  of 
nuts  per  year.  One  of  these  trees  is  estimated  to  be  at  least  1,000  years  old.  See 
Gardners'  Chronicle,  London,  1852,  p.   568;   1857,  p.   694;   1877,  p.  310. 


126  UNIVERSITY   OF   CALIFORNIA — EXPERIMENT   STATION. 

orchard  form.1  If  walnut  trees  could  be  obtained  which  would  average 
200  pounds  of  good  nuts  per  tree  in  the  orchard,  the  profits  from  such 
a  planting  would  probably  equal  the  average  returns  from  citrus  groves, 
while  300  pound  trees  would  be  even  better  than  the  latter  in  the  long 
run.  Since  such  trees  already  exist  in  individual  cases,  there  is  no 
reason  to  doubt  that  it  may  ultimately  be  possible  to  produce  commer- 
cial orchards  of  this  sort. 

During  the  many  years  during  which  the  walnut  has  been  under 
domestication,  both  in  the  old  world  and  the  new,  it  has,  like  all  other 
cultivated  plants,  come  to  vary  to  a  large  extent  in  individual  trees 
in  regard  to  the  characteristics  of  the  tree,  and  particularly  in  regard 
to  the  size,  form,  flavor  and  other  qualities  of  its  fruit.  Likewise,  as 
with  other  crops,  certain  individuals  of  superior  merit  of  one  sort  or 
another  have  been  noted  from  time  to  time,  and  many  such  individ- 
uals have  been  given  definite  names  as  special  varieties  and  the 
peculiar  properties  of  these  varieties  have  been  perpetuated  by  bud- 
ding or  grafting.  In  this  way  we  have  many  definite  varieties  of  the 
walnut,  just  as  with  the  apple,  peach  and  other  fruits.  In  a  broader 
way,  the  walnut  has  also  become  broken  up  into  certain  more  or  less 
well-defined  types,  which  come  true  to  a  certain  extent  from  seed. 

OTHER  SPECIES  OF  WALNUT. 

A  considerable  number  of  walnut  species  is  found  in  various  portions 
of  the  world,  in  addition  to  the  cultivated  form,  Juglans  regia.  "Jug- 
lans is  now  confined  to  the  temperate  and  southern  parts  of  North 
America,  the  Antilles,  South  America  from  Venezuela  to  Peru,  the 
Caucasus,  Persia  and  northwestern  India,  Manchuria,  northern  China, 
and  Japan.  About  ten  species  are  known;  two  are  widely  distributed 
in  the  forests  of  eastern  North  America;  one  inhabits  western  Texas, 
New  Mexico,  and  Arizona,  ranging  far  south  into  Mexico,  where  one 
and  perhaps  two  other  species  occur;  and  one  inhabits  the  valleys  of 
western  California.  The  flora  of  the  Antilles  contains  a  single  species 
of  Juglans,  while  two  or  perhaps  three  others  occur  in  the  northern 
and  western  countries  of  South  America.  In  the  old  world  the  genus 
is  represented  by  Juglans  regia,  an  inhabitant  of  southeastern  Europe 
and  western  Asia  and  now  cultivated  in  all  temperate  countries,  by 
Juglans  mandshurica  of  the  Amur  valley  and  northern  China,  and 
by  Juglans  sieboldiana  of  Japan."* 


JThe  famous  Payne  tree,  near  San  JosS,  has  produced  over  700  pounds  of  nuts  in 
one  year,  but  this  is  a  large  black  walnut  tree,  topworked  in  the  branches. 
*  Sargent,   Silva  of  North  America. 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA. 


127 


Fig.  3. — Black  walnuts.  1,  Southern  California  {calif ornica)  ;  2,  Arizona  (major)  ; 
3,  five  different  types  of  rupestris  from  Texas  and  New  Mexico ;  4,  Northern 
California    (hindsii)  ;   5,   Eastern    (nigra). 


128  UNIVERSITY   OF   CALIFORNIA— EXPERIMENT   STATION. 

AMERICAN  BLACK  WALNUT. 

(Juglans  nigra.) 

This  is  the  native  walnut  of  the  Middle  West,  occurring  in  river 
bottoms  and  valleys  from  western  Massachusetts  to  Minnesota,  south- 
ward to  Georgia,  Florida,  Mississippi,  and  Texas,  and  forming  one  of 
the  finest  trees  of  Ohio,  Illinois,  Nebraska,  Kansas,  Kentucky,  western 
Pennsylvania  and  other  portions  of  the  Middle  West.  It  is  a  tall, 
erect-growing  tree  with  a  large,  straight  trunk  covered  with  deeply- 
furrowed,  narrow-ridged  bark.  The  fruit  is  large,  with  a  thick  husk, 
containing  a  nut  which  is  of  brown  or,  when  dry,  nearly  black  color, 
with  a  hard,  thick  shell  marked  on  the  surface  with  deep,  narrow  fur- 
rows and  prominent,  irregular  ridges.  This  tree  is  not  native  to  Cali- 
fornia, but  was  brought  here  by  the  first  settlers  from  the  East,  and 
has  been  planted  quite  abundantly  since  the  early  fifties.  In  California 
the  true  eastern  species  is  of  very  slow  growth  during  its  early  years, 
and  is  distinguished  from  all  others  by  its  very  rough  nuts.  Other 
conspicuous  characteristics  are  the  fact  that  it  is  extremely  late  in 
coming  out  in  the  spring,  the  trees  remaining  bare  and  dormant  long 
after  other  walnuts  are  in  full  leaf,  while  at  the  same  time,  it  is  one 
of  the  first  to  drop  its  foliage  in  the  fall.  Typical  trees  of  the  true 
Juglans  nigra,  grown  from  seed  introduced  from  various  Middle  West 
States,  may  be  found  growing  about  almost  all  of  the  older  towns  of 
the  State,  particularly  in  the  central  and  northern  portions. 


CALIFORNIA  BLACK  WALNUT. 

The  first  American  explorers  of  California  found  growing  here  native 
walnut  trees  which  have  been  variously  classified  by  botanists.  Sereno 
Watson1  in  1875  described  Juglans  calif ornica  as  "A  large  shrub  or 
tree  in  the  vicinity  of  San  Francisco,  growing  40  to  60  feet  high  and 
2  to  4  feet  in  diameter,  and  ranging  southward  to  Santa  Barbara, 
southern  Arizona  and  Sonora."  He  includes  in  this  species  what 
Torrey  had  previously  described  as  Juglans  rupestris,  var.  major, 
stating  that  "The  more  eastern  Juglans  rupestris  is  but  6  to  20  feet 
high,  with  more  numerous  and  usually  more  acuminate  leaflets,"  etc. 
To  the  latter  species  he  also  ascribes  a  smaller,  thicker  walled  nut  than 
that  of  calif  ornica.  Most  of  the  standard  works,  such  as  those  of  Sar- 
gent and  Britton,  follow  this  arrangement,  giving  the  one  species  Jug- 
lans calif  ornica  for  this  State,  with  a  range  extending  over  most  of 
the  State.     Britton2  states,  for  instance,  page  220,  that  "This  walnut 


^roc.  Am.  Acad.  Arts  and  Sc.  Vol.  10:349,  1875. 
2North  American  Trees. 


Bulletin  231]  WALNUT   CULTURE   IN   CALIFORNIA.  129 

occurs  in  river  bottoms  and  stream  banks  in  western  California,  extend- 
ing from  Los  Angeles  County  northward  to  Napa  County.  It  is  a  very 
beautiful  tree,  attaining  a  height  of  60  feet,  with  a  trunk  diameter  of 
20  inches.     Sometimes,  however,  it  is  reduced  to  a  shrub." 

Locally  it  has  long  been  noted  that  there  are  in  California  two  more 
or  less  distinct  species  of  native  walnut,  that  of  the  north  and  that  of 
the  south.  Some  have  classed  the  southern  form  as  Juglans  rupestris, 
but  very  little  observation  is  necessary  to  show  that  the  native  walnut 
of  southern  California  is  not  that  which  is  included  under  this  name. 
Jepson,1  in  the  Bulletin  of  the  Southern  California  Academy  of  Sci- 
ences, discusses  this  matter,  concluding  that  "Watson  undoubtedly  had 
in  mind  the  southern  California  form,  and  that,  therefore,  this  must 
be  taken  as  the  type  of  Juglans  calif ornica.  For  the  northern  form  he 
proposes  the  name  Juglans  calif  ornica,  var.  hindsii,  naming  it  in  honor 
of  Richard  Brinsley  Hinds,  botanist  of  the  Sulphur  Expedition,  who 
first  discovered  the  California  walnut  on  the  lower  Sacramento  River 
in  1837.  In  a  later  work  Jepson2  again  classes  all  the  California  native 
walnuts  under  the  species  calif  ornica,  stating  that  ' '  The  northern  form, 
named  var.  Hindsii — Jepson,  is  characterized  by  its  distinctly  arbore- 
ous form,  tall  trunks  and  larger  fruits  (1J  to  2  inches  in  diameter). 
Such  differences  may  be  readily  attributable  to  the  climatic  and  soil 
conditions  of  the  northern  habitat. ' ' 

The  study  of  the  native  California  black  walnut  having  become  of 
considerable  importance  in  this  work  in  connection  with  the  subject 
of  rootstocks  for  the  English  walnut,  we  have  given  no  little  attention 
to  an  effort  to  determine  the  true  relationships  of  the  black  walnuts 
found  growing  in  various  portions  of  the  State.  As  Jepson  and  others 
have  noted,  there  is  a  marked  segregation  of  these  trees  into  the  north- 
ern or  central  and  the  southern  portions  of  the  State,  with  a  broad  ter- 
ritory between,  in  which  it  is  evident  that  at  the  present  time  at  least 
no  native  walnuts  occur. 


NORTHERN  CALIFORNIA  BLACK  WALNUTS. 

In  the  upper  portion  of  the  State  no  tree  is  more  conspicuous  as  a 
shade  and  street  tree,  especially  about  the  older  towns,  than  that  which 
is  called  the  California  black  walnut.  Among  these  may  be  found  many 
specimens  of  the  eastern  walnut,  Juglans  nigra,  which  may  be  easily 
identified  by  their  rough  nuts,  late  development  in  spring  and  early 
shedding  of  the  leaves  in  the  fall.  Excluding  these,  there  remain 
very  numerous  specimens  of  the  so-called  true  California  walnut,  a 

^ITol.  VII,   No.    1,   p.    23,    1908. 
2The  Silva  of  California. 

2—231 


130 


UNIVERSITY   OF   CALIFORNIA— EXPERIMENT   STATION. 


tall,  erect-growing  tree,  having  somewhat  smaller  leaves  and  nuts  and 
smoother  bark  than  the  eastern  species,  with  nuts  the  surface  of  which 
is  almost  perfectly  smooth.  This  type  is  popularly  supposed  to  be 
native  to,  and  commonly  distributed  in,  the  northern  half  of  the  State. 
Inquiry  soon  develops,  however,  that  the  majority  of  these  trees  have 
been  planted  where  they  now  stand  within  the  memory  of  people  still 
living. 


Fig.  4. — Northern  California  black  walnuts,  south  of  Gilroy. 

In  this  way,  the  history  of  numerous  very  fine,  large,  old  trees  can 
be  ascertained,  the  oldest  of  which  are  invariably  found  to  have  been 
planted  between  1850  and  1860.  Such,  for  instance,  are  the  two  very 
large  trees  standing  by  the  roadside  just  south  of  Gilroy,  and  numer- 
ous specimens  about  San  Jose,  Hayward,  Stockton,  Vacaville,  Win- 
ters, Suisun,  Santa  Rosa,  Napa,  Colusa,  Marysville,  Yuba  City,  Chico, 
Tehama,  and  many  of  the  old  mining  and  commercial  towns  of  the 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  131 

western  slope  of  the  Sierra  Nevada,  the  San  Joaquin  Valley,  and 
on  both  sides  of  the  Sacramento  Valley.  In  each  and  every  case  the 
history  and  original  planting  of  these  old  trees,  which  represent  the 
largest  California  black  walnut  trees  in  the  State,  can  be  definitely 
ascertained.  In  his  investigations  on  the  subject  Jepson  found  two 
localities  where  this  tree  appeared  to  have  been  growing  naturally  at 
the  time  of  the  advent  of  the  first  white  settlers.  On  this  point  he 
states  as  follows:*  "There  are  two  centers  of  distribution,  one  in  the 
north  and  one  in  the  south,  without  connecting  localities  so  far  as  I 
have  been  able  to  determine.  In  the  north  it  occurs  in  the  lower  Sac- 
ramento region,  keeping  to  the  banks  of  the  river  islands  of  Andrus, 
Grand,  and  others,  and  along  streams  in  the  valleys  at  the  western  base 
of  Monte  Diablo,  specifically  on  Walnut  Creek  and  Lafayette  Creek. " 
In  our  investigations  conclusions  were  reached  coinciding  with  Jep- 
son's,  that  these  were  two  of  the  original  homes  of  the  northern  Cali- 
fornia black  walnut,  and  a  third  location  was  added  to  the  list  which 
appeared  to  be  older  than  either  of  the  other  two.  This  was  a  station 
known  locally  as  Walnut  Grove,  situated  on  the  east  slope  close  to  the 
top  of  the  first  divide  east  of  Napa,  near  Atlas  post  office.  In  this 
locality  there  exists  along  the  mountain-side,  near  the  top,  a  series  of 
small  ponds  or  marshes,  each  consisting  of  a  cup-like  depression  or  ter- 
race in  the  hillside,  about  the  edges  of  which  discharge  several  springs. 
Each  of  these  terraces  no  doubt  contained  at  one  time  a  small  body  of 
water,  but  in  the  course  of  time  they  have  filled  up  with  vegetation 
and  soil  into  swamps  and  mud  holes.  There  are  some  eight  or  ten  of 
these  formations  scattered  along  the  hillside  within  a  mile  or  so,  the 
largest,  the  northernmost  one,  having  an  area  of  possibly  three  or  four 
acres.  The  whole  hillside  throughout  this  locality  is  covered  with  a 
dense  growth  of  native  trees  characteristic  of  the  region,  particularly 
the  Oregon  maple  and  black  oak,  with  California  laurels  and  madrones 
in  the  deeper  canons.  The  soil  is  deep  and  moist  upon  this  slope,  and 
all  vegetation  is  very  luxuriant.  On  the  largest  and  northernmost  of 
the  little  basins  mentioned  there  stand,  near  the  north  end,  three  large, 
black  walnut  trees,  one  of  which  appears  to  be  by  far  the  oldest  wal- 
nut tree  in  the  State.  This  consists  really  of  a  group  of  seven  good 
sized  trees,  all  arising  from  a  common  base,  which  evidently  are  sprouts 
or  second-growth  from  the  stump  of  a  still  older  tree.  The  individual 
stems  in  this  group  form  very  tall,  clean  trunks,  as  upright  and  tree- 
like in  form  as  the  best  type  of  the  eastern  walnut.  The  other  two 
trees  in  this  group  ■  have  single  trunks  at  the  base,  growing  up  with 
clean,  erect  trunks  and  lofty,  spreading  tops.  They  resemble  the  first 
mentioned  tree  in  most  respects,  save  that  one  of  them  has  deeply  fur- 


*Bulletin  of  the  Southern  California  Academy  of  Science,  Vol.  1,  p.  23,  1908. 


132 


UNIVERSITY   OF   CALIFORNIA— EXPERIMENT   STATION. 


rowed  bark  much  resembling  that  of  Juglans  nigra.  All  of  these  trees 
bear  medium  sized,  almost  perfectly  smooth  nuts,  similar  to  those  of 
the  northern  California  black  walnut  trees  found  growing  about  the 
various  towns  mentioned  above.    It  is  evident  at  first  sight  that  these 


Fig.  5. — Old  black  walnut  tree  at  Walnut  Grove,  Napa  County. 

are  very  old  and  on  the  decline.    They  are  gradually  dying  all  over  the 
tops  and  large  limbs  are  breaking  off  and  falling  to  the  ground. 

Around  each  of  the  other  basins  in  the  hillside  is  found  a  group  of 
similar  trees,  some  with  single  trunks,  others  composed  of  several  stems 


Bulletin  231]  WALNUT    CULTURE   IN   CALIFORNIA.  133 

coming  from  a  common  base.  Other  trees  are  found  in  considerable 
numbers  scattered  here  and  there  through  the  forest  and  about  the  hill- 
side between  the  springy  basins.  Quite  a  number  of  these  scattering 
trees  have  recently  been  cut  for  wood.  Altogether  there  are  several 
hundred  of  the  trees.  Evidently  they  have  seeded  spontaneously  from 
the  older  ones  and  become  distributed  over  an  area  of  about  a  square 
mile  by  natural  means.  The  impression  gained  at  present,  however, 
from  all  these  trees,  is  that  they  are  no  longer  reproducing  to  any 
extent,  but  are  gradually  dying  out.  There  is  hardly  a  specimen  less 
than  at  least  twenty  years  of  age,  or  possibly  fifty  years  might  be  nearer 
the  truth.  All  the  older  trees  are  dying  back  and  breaking  down  and 
show  very  little  vigorous,  new  development.  The  latter  is  seen  only  in 
the  case  of  those  trees  which  have  been  cut  down  during  the  last  two  or 
three  years.  In  these  cases  a  very  vigorous  crop  of  sprouts  has  been  sent 
up  from  each  stump. 

Examination  of  the  stumps  of  some  of  these  cut-off  trees  shows  one 
that  many  of  them  were  more  than  one  hundred  years  of  age  when  cut, 
and  this  is  true  even  of  some  of  the  smaller  ones.  Some  may  be  found 
which  are  considerably  older  than  this  and  apparently  well  up  toward 
two  hundred  years  old.  The  broken  off  stem  shown  in  the  picture  of 
the  largest  tree  was  cut  off  and  found  to  be  at  least  sixty  years  of  age, 
and  probably  considerably  older  than  this  at  the  base.  This  was  much 
the  smallest  of  the  trunks  in  this  group. 

The  little  glade  in  which  this  tree  stands  was  evidently  the  site  of 
an  Indian  village,  as  evidenced  by  numerous  arrow  heads,  spear  points, 
mortars,  etc.,  which  have  been  found  there.  On  investigation  these 
trees  show  beyond  all  possible  doubt  that  many  of  them  must  have  been 
large,  old  trees  even  at  the  time  of  the  Spanish  occupation  of  Cali- 
fornia, and  that  they  could  not  have  been  planted  by  any  white  people. 
This  grove  can  be  most  readily  reached  by  driving  from  Napa  to  Wil- 
son's Inn,  a  summer  resort,  at  which  is  located  Atlas  post  office,  and 
from  which  a  wood  road  leads  down  to  the  walnut  trees  at  a  distance 
of  about  two  miles. 

A  few  miles  southeast  of  this  grove,  on  the  old  Combs  ranch  in  Gor- 
don Valley,  there  stand  several  black  walnut  trees,  one  of  which  is  par- 
ticularly large;  early  settlers  state  that  this  tree  existed  from  their 
earliest  recollection,  but  that  they  can  remember  it  as  a  comparatively 
small  tree.  It  is,  therefore,  probably  older  than  any  of  the  trees  planted 
about  the  towns  during  the  past  sixty  years,  but  younger  than  those 
upon  the  mountain-side,  from  which  it  presumably  descended.  One 
of  the  oldest  residents  of  this  region,  Mr.  Joe  Gordon,  of  Gordon  Val- 
ley, was  interviewed  in  regard  to  the  history  of  these  trees.  Mr.  Gordon 
is  of  Spanish  descent  and  was  born  and  has  always  lived  in  this  vicin- 


134 


UNIVERSITY  OF  CALIFORNIA— EXPERIMENT   STATION. 


Bulletin  231]  WALNUT   CULTURE   IN   CALIFORNIA.  135 

ity,  being  now  a  man  of  advanced  age.  Mr.  Gordon  stated  that  the  one 
tree  just  mentioned  had  existed  as  long  as  he  could  remember,  but  he 
could  recollect  it  as  a  small  tree  in  his  boyhood.  In  the  grove  on  the 
mountain-side,  he  stated,  there  were  old  trees  as  large  as  any  which 
are  there  now  as  far  back  as  he  could  remember  in  his  earliest  boyhood. 
Several  of  the  earliest  American  settlers,  whose  memory  goes  back  for 
nearly  sixty  years,  make  the  same  statement  in  regard  to  these  trees. 

The  history  of  the  two  stations  mentioned  in  the  quotation  from 
Jepson  has  been  quite  thoroughly  investigated  in  connection  with  this 
work.  In  regard  to  the  one  mentioned  near  the  base  of  Mount  Diablo, 
we  may  say  that  in  the  valleys  on  the  west  side  of  the  mountain  in 
the  vicinity  of  the  towns  of  Walnut  Creek,  Danville,  Lafayette  and 
Concord,  there  are  a  great  many  California  black  walnut  trees,  both 
young  and  old,  most  of  which  have  been  planted  within  the  memory 
of  people  still  living  in  that  vicinity.  Inquiry  shows,  however,  that 
there  was  one  locality  in  this  region  where  black  walnut  trees  were 
growing  when  the  first  white  people  arrived  in  the  country.  This  is 
evidenced  by  the  memory  of  various  old  settlers,  also  by  the  name 
" Walnut  Creek,"  and  the  fact  that  the  original  Spanish  grant  com- 
prising this  region  bore  the  name  ' '  Eancho  Arroyo  de  las  Nueces  y  Bol- 
bones."  "This  fact,"  to  quote  from  Mr.  Ely  Hutchinson,  "is  con- 
firmation strong  as  proofs  of  holy  writ  that  the  walnut  was  growing 
in  the  vicinity  when  the  Mexicans  sent  in  their  petition  for  the  grant. ' ' 
The  name  "Bolbones"  appears  to  be  at  present  quite  obscure,  but, 
according  to  the  investigations  of  Mr.  Hutchinson,  it  probably  refers 
to  some  other  kind  of  tree  which  grew  in  that  vicinity.  The  original 
trees  of  this  locality  were  located  in  the  so-called  ' '  Moraga  Valley ' '  in 
the  Walnut  Creek  country  east  of  Oakland.  Some  of  these  trees  are 
still  standing,  although  many  of  the  finest  were  cut  for  timber  many 
years  ago.  These  trees  are  of  an  extremely  stately,  tall-growing,  clean- 
trunk  type,  fully  as  much  so  as  the  best  types  of  the  eastern  walnut, 
Juglans  nigra.  They  are  all  composed  of  single  trunks  and  have  the 
appearance  of  being  younger  than  the  oldest  trees  in  the  Napa  Moun- 
tains. The  bases  of  them  are  larger  than  any  of  the  trees  in  the  latter 
locality,  being  in  good,  moist,  deep  soil  in  an  open  valley,  free  from 
the  competition  of  other  trees.  The  nuts  and  foliage  are  entirely  sim- 
ilar to  those  of  the  Napa  County  trees. 

The  third  original  locality  mentioned  is  that  in  the  vicinity  of  the 
town  of  Walnut  Grove  on  the  Sacramento  River,  about  thirty  miles 
south  of  Sacramento  city.  Large,  old,  black  walnut  trees  are  very 
abundant  on  the  ranches  in  this  locality,  and  there  was  until  quite 
recently  a  long  row  of  large,  fine,  old  trees  along  the  river  bank  out- 
side the  levee  from  Walnut  Grove  north.     These  trees  were  cut  down 


136  UNIVERSITY   OF   CALIFORNIA— EXPERIMENT   STATION. 

a  few  years  ago  in  repairing  the  levee.  Although  very  large,  they  were 
not  the  original  trees  of  that  locality,  but  were  planted  there  within 
comparatively  recent  times.  Inquiry  in  the  vicinity  of  Walnut  Grove 
has  developed  the  information  that  when  the  first  American  settlers 
came  to  the  lower  Sacramento  there  were  a  great  many  black  walnut 
trees  growing  in  this  vicinity.  Mr.  William  Holtlum,  who  at  the  time 
of  this  investigation  was  thought  to  be  about  the  oldest  living  settler 
in  the  vicinity  of  Walnut  Grove,  came  there  about  1850.  At  that  time, 
he  stated,  there  was  quite  a  large  grove  of  magnificent  black  walnut 
trees  growing  at  and  below  the  fork  of  the  river  just  below  Walnut 
Grove.  There  were  twenty  or  more  trees  there  over  three  feet  in  diam- 
eter. Black  walnut  trees  were  scattered  all  along  the  river  from  Free- 
port  to  Rio  Vista,  growing  on  the  higher  spots  on  the  river  bank  rather 
than  in  the  more  swampy  land  further  back  from  the  river. 

On  what  is   now  the   Hart  place,   near  Isleton,   there   were  some 
especially  large  trees.     The  row  of  trees  which  stood  along  the  river 
near  Walnut  Grove  was  planted  by  one  H.  W.  O'Dell.     The  earliest 
planting  was  probably  about  1856,  followed  by  others  up  to  the  early 
sixties.     During  the  early  fifties  many  people  used  to  come  to  Wal- 
nut Grove  from  the  country  about  Vacaville,  Elmira,  and  other  places, 
and  carried  away  walnuts  by  the  bushel  and  sack.     Up  and  down  the 
river  there  was  a  great  growth  of  live  oak,  white  oak,  ash,  cotton- 
wood  and  black  walnut  until  1856,  when  a  great  fire  from  the  north 
swept  over  the  whole  country  destroying  almost  all  the  native  tim- 
ber. .  .     Mrs.  Clara  Lord,  of  Walnut  Grove,  stated  that  her  parents 
came  to  this  locality  in  1850  and  set  up  a  tent  under  three  walnut  trees 
which  stood  in  front  of  her  present  house.    There  were  also  many  other 
large  black  walnut  trees  in  the  locality  at  that  time.  .  .    Mr.  Joe  Wise 
stated  that  he  chopped  wood  on  the  river  in  1853  and  '54,  and  chopped 
down  many  walnut  trees  2-J  feet  and  more  in  diameter.  .  .    Mr.  Robert 
Sharp,  of  Walnut  Grove,  stated  that  he  came  to  the  vicinity  in  1851, 
when  a  boy,  but  remembers  very  distinctly  that  there  were  many  large 
walnut  trees  growing  along  the  river  at  that  time.    Also  that  they  had 
to  cut  their  way  in  with  axes  on  account  of  the  luxurious  vegeta- 
tion. .  .    Mr.  Joe  Greene,  living  two  miles  above  Courtland,  stated  that 
in  the  early  days  they  cut  out  black  walnut  trees  two,  three  and  four 
feet  in  diameter.     Also  that  such  trees  grew  among  the  timber  along 
the  river  bank  rather  than  back  in  the  swamps,  and  that  they  extended 
south  as  far  as  Rio  Vista.  .  .    Mr.  C.  V.  Talmage  came  to  this  region 
in  1857,  and  stated  that  there  were  many  immense  black  walnut  trees 
along  the  river  at  that  time.    He  has  trees  on  his  place  of  immense  size, 
which  were  planted  in  1858.  .  . 

This  data  is  sufficient  to  show  that  there  was  an  abundant  growth 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  137 

of  black  walnut  trees  at  this  point  previous  to  the  first  white  settle- 
ment. Apparently,  none  of  the  original  trees  now  remain  in  this  local- 
ity, although  some  of  the  largest  black  walnut  trees  in  the  State  may 
be  found  here,  having  been  planted  in  the  fifties.  These  trees  and  the 
nuts  which  they  bear  are  of  exactly  the  same  type  as  those  at  Walnut 
Creek  and  at  Walnut  Grove  in  the  Napa  Mountains. 

It  is  not  improbable  that  other  localities  of  this  sort  may  be  found  in 
the  northern  part  of  the  State,  especialy  in  northeastern  Napa  County 
where  we  have  a  fairly  definite  report  of  such  original  trees. 

As  to  the  oldest  trees  standing  in  the  vicinity  of  the  various  towns 
mentioned,  the  history  of  almost  all  of  them  can  be  ascertained.  In 
regard  to  the  two  large  trees  south  of  Gilroy,  for  instance,  which  are 
some  of  the  largest  in  the  State,  Judge  S.  F.  Leib,  of  San  Jose,  writes 
us  as  follows:  "I  was  informed  by  Mr.  Zuck  (now  deceased),  who 
examined  into  the  matter  for  me,  that  the  two  large  native  California 
black  walnut  trees  about  a  half  mile  south  of  Gilroy  fronting  on  the 
public  road  were  planted  in  1856  or  1857  by  Mr.  Reeve.  I  measured 
them  last  fall  and  found  each  of  them  to  be  over  four  feet  in  diameter. ' ' 
About  San  Jose  there  are  trees  still  older  than  these,  most  or  all  of 
which  appear  to  have  been  planted  from  nuts  obtained  at  Walnut 
Creek.  About  Stockton  most  of  the  oldest  trees  seem  to  have  come 
from  Walnut  Grove  on  the  Sacramento  River.  In  Suisun  Valley  there 
are  some  particularly  large,  fine  old  trees  on  the  Matthew  Wolfskill 
ranch  and  others,  planted  in  the  fifties.  The  nuts  from  which  these 
trees  grew  came  mostly  from  Walnut  Creek.  There  are  some  very 
large  trees  on  the  Dan  Berry  place  in  the  same  vicinity.  These  are 
thought  to  have  been  planted  in  the  early  fifties  from  Walnut  Creek 
nuts.  In  the  vicinity  of  Vacaville  there  are  numerous  old  trees ;  one  on 
the  W.  B.  Davis  ranch  east  of  Vacaville  is  said  by  Mr.  Davis  to  have 
been  a  natural  seedling  in  Gordon  Valley,  Napa  County,  which  was 
moved  to  Vacaville  in  1853.  This  is  the  largest  tree  on  the  place,  stand- 
ing just  south  of  the  Japanese  bunk  house.  Mr.  Davis  states  that  he 
grew  a  nursery  in  1860  from  nuts  obtained  at  Walnut  Grove  on  the 
Sacramento  River,  and  that  most  of  the  old  trees  about  Vacaville  came 
from  this  planting.  When  he  obtained  the  nuts  there  were  many  trees 
at  Walnut  Grove  three  to  four  feet  in  diameter.  On  the  Thurber  place 
in  Pleasant  Valley,  between  Vacaville  and  Winters,  there  are  two  large 
trees  in  front  of  the  house  at  the  front  gate  and  one  north  of  the  house 
which  were  grown  by  Mr.  Hough  on  the  Joe  Bassford  place.  He  got 
the  nuts  from  Napa  County,  supposedly  from  wild  trees.  The  long 
rows  of  black  walnuts  on  both  sides  of  the  road  near  the  Fred  Buck 
place,  most  of  which  have  been  worked  over  into  English  walnuts,  came 
from  the  Wolfskill  place  near  Winters.     On  the  latter  places,  that  of 


138  UNIVERSITY  OF  CALIFORNIA— EXPERIMENT  STATION. 

John  Wolfskill  east  of  the  road  and  that  of  his  brother  on  the  west 
side,  there  are  a  great  many  old  California  black  walnut  trees,  the  old- 
est being  a  row  along  the  creek  bank  to  the  northwest  of  the  road. 
These  trees,  according  to  a  statement  of  Mrs.  S.  "Wolfskill,  were  planted 
about  1855  by  a  man  named  McMahan,  from  nuts  obtained  in  the 
mountains  east  of  Napa.  (Presumably  from  the  trees  which  we  have 
described.)  Mrs.  Wolfskill  states  that  all  the  black  walnut  trees  in  this 
vicinity  originated  from  this  planting.  According  to  the  recollection 
of  her  sons,  Joe  and  Will,  however,  John  Wolfskill  brought  walnuts 
from  the  Sacramento  River  about  1860  and  planted  them  on  the  ranch. 
Mr.  W.  W.  Smith,  of  Vacaville,  recollects  that  a  man  by  the  name  of 
Percy  Wiggins,  who  formerly  lived  in  Napa,  told  him  that  he  found 
walnuts  growing  wild  in  Conn  Valley  in  the  northern  part  of  Napa 
Valley,  and  planted  a  nursery  of  these  about  1858.  He  sold  all  these 
trees  but  one  and  allowed  this  one  to  grow  where  it  stood,  which  was 
in  Browns  Valley  west  of  Napa.  Mr.  Smith  took  nuts  from  this  tree 
in  1873  and  raised  the  trees  which  stand  along  the  road  on  what  is  now 
the  Henry  Bassford  place  near  Vacaville,  which  trees  were  cut  off  and 
worked  over  to  English  walnuts  after  they  were  a  foot  or  more  in 
diameter. 

We  need  not  occupy  our  space  with  further  details  of  this  sort,  hav- 
ing given  enough  of  this  historical  matter  to  show  that  the  origin  of 
most  of  these  old  trees  can  be  traced  by  inquiry  among  old  settlers. 


SOUTHERN  CALIFORNIA  TYPE. 

In  the  southern  part  of  the  State  black  walnut  trees,  apparently 
indigenous,  are  found  growing  over  a  considerable  area,  and,  contrary 
to  the  case  in  the  northern  part  of  the  State,  very  few  such  trees  have 
been  planted  out  along  roadsides  or  for  ornament.  The  southernmost 
point  at  which  the  tree,  to  our  knowledge,  is  found  growing  is  in  the 
Santiago  Canon  east  of  the  city  of  Orange.  From  this  point  north  it 
occurs  sparingly  near  the  mouth  of  the  Santa  Ana  Canon,  abundantly 
in  Brea  Canon  along  the  road  between  Fullerton  and  Pomona,  and 
scattered  through  various  canons  in  the  Puente  hills  west  of  this  road. 
It  is  quite  abundant  in  the  San  Jose  hills  west  of  Pomona,  especially 
in  the  so-called  Walnut  Wash,  which  extends  down  toward  Covina. 
The  species  is  scattered  sparingly  along  the  southern  base  of  the  high 
mountains  from  the  Cajon  Pass  above  San  Bernardino  to  Garvanza, 
near  Los  Angeles.  In  the  Santa  Monica  Mountains  the  tree  is  abun- 
dant, especially  on  the  northern  slopes,  near  Lankershim,  near  the  north 
opening  of  the  Cajuenga  Pass,  and  in  all  canons  through  this  range  on 


Bulletin  231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


139 


both  sides  to  its  northern  extremity  near  Hueneme.  The  tree  is  abund- 
ant along  both  branches  of  the  Southern  Pacific  Railroad  between  Bur- 
bank  and  Ventura  and  in  the  intervening  country.  That  is  to  say,  it 
occurs  in  the  vicinity  of  Chatsworth,  Simi,  and  Moorpark,  in  the  hills 
north  of  the  latter  places,  in  the  next  valley  north  near  Newhall  and 
on  down  the  valley  through  Camulos,  Fillmore  and  Santa  Paula,  and 
in  the  foothills  to  the  north  of  this  valley  (Santa  Clara  Valley  of  the 


Fig.   7. — Native  southern  California  black  walnuts,  Brea  Canon. 


south).  Going  farther  north,  the  tree  is  not  seen  near  the  railroad, 
but  is  abundant  in  the  foothills  up  into  the  Ojai  Valley  back  of  Ven- 
tura, and  scattered  along  the  foothill  range  back  of  Ventura  and  Car- 
pinteria,  north  of  which  point  near  Santa  Barbara  the  species  begins 
to  grow  scarce.  Mr.  C.  W.  Beers  states  that  Mr.  Ellwood  Cooper  has 
pointed  out  to  him  trees  which  were  undoubtedly  growing  wild  in  the 
canons  back  of  Mr.  Cooper's  ranch  some  twenty  miles  north  of  Santa 
Barbara.     From  this  point  north  we  know  of  no  well  authenticated 


140 


UNIVERSITY   OF  CALIFORNIA — EXPERIMENT   STATION. 


record  of  native-growing  black  walnut  trees  until  we  reach  those  at 
Walnut  Creek  near  Mount  Diablo,  a  distance  of  about  three  hundred 
and  fifty  miles.  "We  have  investigated  various  reports  of  indigenous 
trees  in  this  stretch  of  country,  but  thus  far  have  found  evidence  of  all 
such  having  been  planted  since  the  American  occupation. 

The  southern  California  trees  are  considerably  different  in  aspect 
from  those  of  the  north,  although  individual  specimens  of  each  may  be 


Fig.   8. 


-Large  southern  California  black  walnut  tree  near  roadside  between  Ventura 
and  Nordhoff. 


found  which  resemble  each  other  quite  closely.  The  southern  tree  is 
much  more  shrubby,  frequently  branching  directly  from  the  ground, 
and  tending  to  break  up  into  a  much  branched,  broad,  low-spreading 
head  even  when  a  single  trunk  is  formed.  It  is  not,  as  is  popularly 
supposed,  a  dwarf  or  slow-growing  tree,  except  in  so  far  as  it  is  influ- 
enced to  develop  in  this  way  by  the  fact  that  it  is  able  to  and  frequently 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  141 

does  grow  upon  dry,  exposed  hillsides  rather  than  in  deep,  rich,  moist 
soil,  to  which  the  original  groves  of  the  northern  California  type  are 
confined.  In  a  similar  situation,  the  southern  California  tree  grows 
rapidly  and  vigorously,  forming  particularly  a  very  thick  trunk,  but 
with  a  round,  bushy  top  rather  than  with  a  single,  erect,  continuous, 
central  axis.  Along  the  road  between  Ventura  and  Nordhoff  and  in 
the  hills  about  the  latter  vicinity,  trees  of  extremely  great  trunk 
diameter  may  be  seen,  but  the  tops  are  very  broad,  low  and  bushy. 
Professor  Jepson  has  well  characterized  this  form  as  "elephantine"  in 
comparison  to  the  erect,  arboreous  habit  of  the  northern  type.  There  is 
an  immense  tree  of  apparently  the  southern  type  on  the  premises  of 
F.  M.  Gifford,  at  No.  18  East  Haley  street,  Santa  Barbara.  This  tree 
is  of  unknown  age  and  over  four  feet  in  diameter.  There  is  another 
extremely  large  one  a  few  miles  northwest  of  Covina,  forming  a  well- 
known  landmark  and  resting  place  by  the  roadside.  Many  other 
instances  could  be  cited  to  show  that  the  southern  California  black  wal- 
nut is  not  at  all  a  dwarf  tree,  but  is  rather  one  of  rapid  growth  and  large 
size  in  diameter  when  growing  under  conditions  at  all  favorable. 

The  nut  of  the  southern  type  varies  considerably  in  size  on  different 
trees,  but  in  general  it  is  much  smaller  than  that  of  the  northern  type. 

Relationship  Between  the  Southern  and  Northern  California  Types  of 
Black  Walnut. — Assuming  that  the  southern  California  type  of  black 
walnut  is  indigenous  to  the  region  where  it  is  found,  which  fact  there  is 
no  reason  to  doubt,  the  question  arises,  whence  came  these  three,  isolated, 
original  groups  of  the  northern  tree  ?  It  is  most  natural  to  agree  with 
Dr.  Jepson  that  these  northern  trees  were  planted  by  the  Indians  many 
years  ago,  either  intentionally  or  by  chance,  with  nuts  which  they  had 
brought  from  the  south  for  food  and  exchange.  Each  of  the  three  local- 
ities is  known  to  have  been  the  site  of  an  abundant  Indian  population, 
and  it  is  also  well  known  that  walnuts  and  other  nuts  were  carried  about 
by  the  Indians  for  such  purposes. 

Mr.  Joe  Gordon,  alluded  to  above,  whose  memory  goes  back  to  about 
1846,  states  that  in  his  youth,  when  Indians  were  abundant  in  Solano  and 
Napa  counties,  they  frequently  used  black  walnuts  with  which  to  trade 
with  the  white  people  for  various  articles  which  they  desired.  On  being 
questioned  as  to  his  idea  of  the  origin  of  the  old  walnut  trees  in  his 
vicinity,  Mr.  Gordon  stated  that  he  had  heard  that  black  walnuts  grew 
wild  in  the  southern  part  of  the  State  and  that  his  idea  had  been  that  the 
Indians  brought  nuts  from  the  south  from  which  these  trees  originated. 
The  more  erect  type  of  tree  and  the  larger  nuts  of  the  northern  type  are 
explained  by  Professor  Jepson  as  an  influence  of  environment. 

In  order  to  obtain  further  light  upon  this  question,  we  commenced 


142 


UNIVERSITY   OF   CALIFORNIA— EXPERIMENT    STATION. 


Fig.    9. — One-year-old   black   walnut   seedlings;    southern   California   on   the   left    (1), 
eastern  in  the  center   (2),  northern  California  on  the  right   (3). 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  143 

several  years  ago  planting  both  southern  and  northern  California  wal- 
nuts side  by  side  in  nurseries  both  in  the  south  and  in  the  north.  When 
so  grown  the  resulting  trees  have  shown  very  marked  and  constant  differ- 
ences from  one  another  and  the  characteristics  of  each  type  as  shown  in 
the  nursery  have  remained  constant  both  in  the  south  and  in  the  north. 
Seedlings  of  the  southern  type  are  much  more  branching  and  bushy  than 
those  of  the  northern,  sending  out  large,  lateral  branches  and  secondary 
stems  close  to  the  ground,  while  the  northern  seedlings  grow  erect  with 
one  stem  and  few  large  laterals.  In  this  way  the  southern  seedlings  are 
broad,  bushy  and  covered  with  foliage  clear  to  the  ground,  in  marked 
contrast  to  the  other  type.  The  leaves  of  the  southern  tree  are  some- 
what smaller,  more  finely  divided  and  with  more  sharply  pointed  leaflets 
than  those  of  the  northern.  They  are  also  a  little  lighter  in  color  and 
the  bark  is  of  a  brighter  green.  One  of  the  most  pronounced  differences 
lies  in  the  fact  that  the  southern  seedlings  come  out  much  earlier  in  the 
spring  and  continue  to  hold  their  foliage  and  grow  much  later  in  the  fall 
than  the  northern,  whether  they  are  planted  in  the  south  or  in  the  north. 
This  is  a  most  decided  difference  and  holds  true  constantly,  the  rows  of 
southern  seedlings  being  always  in  full  leaf  in  the  spring  while  the 
northern  are  still  bare,  and  showing  the  same  condition  in  the  fall  for 
several  weeks  after  the  northern  California  seedlings  have  dropped  all 
their  leaves.  This  characteristic  is  one  upon  which  environment,  in  the 
first  generation  at  least,  has  no  apparent  effect.  In  the  germination  of 
the  nuts  the  two  forms  also  show  a  difference.  Nuts  of  the  southern 
California  type  are  much  quicker  to  germinate  in  the  spring  and  when 
planted  in  the  same  conditions  invariably  sprout  much  earlier  than  the 
northern  nuts,  whether  they  be  planted  in  the  north  or  south. 

Another  decided  difference  lies  in  the  relative  effect  upon  trees  of  the 
two  forms  of  various  conditions  such  as  dryness,  heat,  etc.  An  appar- 
ently physiological  disease,  which  we  will  discuss  later,  called  the  "  yel- 
lows "  or  ' '  frizzles, ' '  affects  the  northern  California  type  very  badly  in 
some  instances,  but  we  have  never  known  a  southern  California  seedling 
to  show  this  disease,  even  though  grown  in  rows  adjoining  badly-affected 
northern  California  trees.  Another  disease,  nursery  root  rot,  see  page 
379,  invariably  picks  out  the  southern  California  black  seedlings,  never 
affecting  those  of  the  northern  type  in  the  same  nursery. 

We  know  of  no  trees  of  the  southern  California  type  of  any  consid- 
erable age  now  growing  in  the  north.  There  are  several  of  these  trees 
about  four  years  of  age  planted  by  Professor  E.  B.  Babcock  on  the  Uni- 
versity grounds  west  of  the  new  agricultural  building,  and  these  trees  are 
of  the  characteristic  bushy-topped  form,  coming  out  early  in  the  spring 
and  holding  their  foliage  very  late  in  the  fall,  in  marked  contrast  to 
trees  of  the  northern  type.  We  have  planted  southern  nuts  in  several 
nurseries  in  the  northern  part  of  the  State  and  found  that  the  resulting 


144  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


Fig.   10. — Young  northern  California  black  walnut  tree,   State  School  grounds, 

Whittier. 


Bulletin  231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


145 


seedlings  retained  all  their  usual  characteristics  in  relation  to  seedlings 
from  northern  California  nuts.  No  effect  whatever  of  environment 
could  be  seen  in  any  of  these  cases.  Of  the  northern  California  walnuts 
in  the  southern  part  of  the  State,  we  know  of  one  considerable  planting 


Fig.   11. — Young  southern  California  black  walnut  tree,  State  School  grounds,  Whittier. 

near  Pasadena  where  the  trees  are  now  old  enough  to  produce  quite  large 
crops  of  nuts.     These  trees  retain  all  the  characteristics  of  the  northern 
California  type  in  regard  to  the  size  of  the  nuts  and  the  time  of  foliation 
and  defoliation. 
3—231 


146  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

Considering  the  characteristic  and  constant  difference  in  the  form  of 
the  trees,  both  in  old  specimens  and  in  the  nursery,  the  most  pronounced 
difference  in  the  vegetative  period  when  the  trees  are  grown  side  by  side, 
and  the  same  difference  under  the  same  circumstances  in  relation  to  the 
diseases  mentioned,  we  feel,  on  the  whole,  extremely  doubtful  as  to  the 
identity  of  the  northern  California  type  with  that  of  the  south.  It 
seems  to  us  certain  that  the  northern  type  is  at  least  a  distinct  variety  of 
the  southern,  in  which  case  Jepson's  classification  of  it  as  Juglans  cali- 
fornica  var.  hindsii  would  be  acceptable.  Still  it  is  remarkable  that  a 
variety  so  uniformly  distinct  from  the  original  type  in  the  larger  size  of 
the  nuts,  the  upright  form  of  the  tree,  later  foliation  and  earlier  defolia- 
tion period,  slower  sprouting  of  the  nuts  and  different  behavior  under 
certain  climatic  conditions  should  comprise  all  the  northern  California 
trees  without  exception.  It  is  also  remarkable  that  so  distinct  a  variety 
should  have  developed  in  the  north  without  the  development  of  any  other 
distinct  varieties  in  the  south  or  other  portions  of  the  State.  Almost 
the  only  way  to  account  for  the  northern  California  type  as  a  variety  of 
the  southern  is  to  assume  that  the  northern  trees  are  all  descended 
originally  from  one  individual  tree,  which  tree  happened  to  be  of  its 
distinct  type. 

We  are  considerably  inclined  toward  another  solution  of  the  question, 
namely,  that  the  northern  California  trees  represent  the  relics  of  an 
almost  extinct  species,  paralleling  the  case  of  several  other  trees  found 
in  California.  In  this  case  the  northern  California  walnut  would  prob- 
ably be  called  Juglans  hindsii  Jepson.  Even  under  this  supposition,  it 
is  true  in  all  probability  that  the  original  trees  of  the  northern  type 
found  in  the  three  localities  mentioned  were  planted  by  the  Indians 
rather  than  representing  an  original,  indigenous  growth.  What,  then, 
the  history  of  the  tree  was  previous  to  these  plantings  and  when  the 
original  planting  in  these  localities  took  place  must  still  remain  a  mys- 
tery. Present  indications  are  that  the  Napa  County  station  is  the  oldest 
of  the  three,  and  it  is  possible  that  the  tree  was  originally  a  native  of 
that  portion  of  the  State  whence  the  nuts  were  carried  by  Indians  to 
other  localities. 


OTHER  NATIVE  WALNUTS  OF  THE  SOUTHWEST. 

In  addition  to  the  California  species  of  black  walnut,  there  have  been 
more  or  less  distinctly  recognized  by  botanists  at  least  two  other  species, 
namely  Juglans  rupestris  and  Juglans  major,  the  range  of  these  forms 
extending  over  Arizona,  New  Mexico,  and  Texas.  Much  uncertainty 
has  prevailed  and  still  exists  as  to  the  identity  and  limits  of  these 
species,  especially  as  to  the  limitations  of  Juglans  rupestris.    By  some- 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  147 

the  latter  species  has  been  held  to  include,  at  least  as  a  variety,  the 
southern  California  type,  while  Juglans  major  has  frequently  been  con- 
sidered a  variety  of  rupestris.  The  general  understanding  of  rupestris 
has  been  that  it  is  a  decidedly  dwarf,  shrubby  type  with  very  small 
nuts,  while  major  has  been  considered  a  larger  and  more  erect  form. 
According  to  Britton,  Juglans  major  is  the  species  indigenous  to  Ari- 
zona, particularly  the  western  portion,  while  the  range  of  rupestris  is 
found  further  eastward  in  New  Mexico  and  Texas.  We  have  not 
studied  this  subject  to  any  extent  from  a  botanical  standpoint,  but  in 
connection  with  our  investigations  on  rootstocks  for  the  English  walnut 
we  have  received  and  planted  nuts  from  all  the  states  just  mentioned, 
and  have  also  through  correspondence  gathered  considerable  informa- 
tion concerning  the  native  black  walnuts  of  these  states.  From  such 
information,  together  with  a  study  of  the  nuts  which  we  have  received 
and  the  trees  grown  therefrom,  we  are  convinced  on  one  point,  namely 
that  Juglans  major  of  western  Arizona  and  Juglans  rupestris  of  New 
Mexico  and  Texas  are  quite  distinct  from  one  another  and  also  distinct 
from  either  of  the  California  types.  It  is  true  that  all  four  of  these 
forms  run  more  or  less  into  one  another,  and  the  question  as  to  whether 
the  differences  between  them  are  of  varietal  or  specific  rank  does  not 
lie  within  the  province  of  the  present  work.  It  is  certain,  however, 
that  in  the  nursery  the  four  forms  are  very  distinct  and  decidedly 
different  from  one  another.  From  our  observations  thus  far  it  would 
appear  that  there  is  as  much  similarity  between  Juglans  major  of  Ari- 
zona and  Juglans  liindsii  of  northern  California  as  between  any  other 
two  of  the  four  types.  Our  observations  in  this  respect,  however,  extend 
only  to  the  general  form  and  appearance  of  the  old  trees,  seedlings,  and 
nuts. 

NATIVE   WALNUTS   OF   ARIZONA. 

Black  walnut  trees  of  an  evidently  indigenous  nature  are  found 
growing  in  various  portions  of  Arizona.  The  Arizona  species  was 
formerly  classified  as  Juglans  rupestris,  with  a  variety  or  second  species 
called  Juglans  major,  the  latter  being  supposedly  a  more  erect  and 
tree-like  type  than  the  true  rupestris.  Professor  J.  J.  Thornber  of  the 
University  of  Arizona  writes  as  follows: 

"We  had  supposed  that  Juglans  rupestris  was  our  common  walnut 
here  and  had  classified  it  as  such.  Last  year,  however,  I  came  to  the 
conclusion  that  our  species,  at  least  a  considerable  amount  of  it,  is 
Juglans  major.  This  is  our  common  walnut  that  grows  in  southern 
Arizona,  and  it  may  be  the  only  species.  Juglans  rupestris,  as  I  under- 
stand it,  grows  in  Texas,  though  of  course  it  may  get  as  far  as  Arizona. ' ' 
Again,  "I  am  sending  you  under  separate  cover  two  quarts  of  nuts  of 


148 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 


Juglans  major,  as  we  call  it.  The  plant  may  be  only  a  form  of  Juglam 
rupcstris."  Again,  "The  tree  (Juglans  major)  is  common  throughout 
southern  Arizona,  in  mountain  canons  and  alluvial  soils  of  flood  plains. 
It  grows  at  as  low  an  altitude  here  as  1,500  feet  and  apparently  as  high 
in  the  mountains  as  8,000  feet,  so  you  see  it  has  a  wide  range. ' ' 


Fig.   12. — Arizona   black   walnut   tree,   Vacaville. 

One  old  tree  which  we  found  growing  in  California,  of  supposedly 
Arizona  origin,  is  of  interest  in  this  connection.  This  is  located  on  the 
home  place  of  Mr.  Harbison,  near  Vacaville,  and  is  a  very  large,  erect 
tree  said  to  have  been  planted  about  1854.  The  story  is  that  Mr.  Har- 
bison's father  crossed  the  plains  in  that  year  and  picked  up  some  wal- 
nuts in  Arizona,  from  one  of  which  this  tree  came.  The  tree  is  of  a 
decidedly  erect,  tree-like  type  writh  none  of  the  dwarf  or  bush  form 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  149 

which  is  supposed  to  belong  to  Juglans  rupestris.  It  is  much  like  the 
northern  California  black  walnut  in  general  appearance,  but  the  nuts 
are  somewhat  smaller  and  more  deeply  grooved  and  the  aspect  of  the 
foliage  slightly  different.  Seedlings  from  this  tree,  and  likewise  those 
grown  from  Arizona  nuts,  are  in  general  appearance  very  much  like 
the  northern  California  type,  being  of  a  rapid  growth,  erect,  with  dark- 
colored  bark  and  no  large  side  branches.  The  tree  is  decidedly  dif- 
ferent in  the  nursery  from  the  supposedly  true  Juglans  rupestris  of 
Texas  and  New  Mexico  and  it  is  therefore  our  conclusion  that  Juglans 
major  is  a  fairly  distinct  species  as  southwestern  black  walnuts  go. 


NATIVE  WALNUTS  OF  TEXAS. 

From  Texas  we  have  received  many  nuts  of  what  we  take  to  be  the 
true  Juglans  rupestris.  These  nuts,  while  varying  greatly  in  size,  are 
smaller  even  than  those  of  the  southern  California  type,  while  some  of 
them  are  extremely  tiny,  averaging  only  about  one  half  inch  in  diameter. 
The  nuts  are  characteristically  marked  by  decidedly  deep,  branching 
grooves,  being  easily  distinguished  in  this  respect  from  the  California 
species  and  from  Juglans  major  of  Arizona.  As  compared  with  nuts 
of  Juglans  nigra  these  are  much  smaller  in  size,  less  abundantly  grooved 
and  not  ridged  like  those  of  the  latter  species.  From  such  nuts  develop 
what  appears  to  be  true  Juglans  rupestris,  a  dwarf,  shrub-like  tree,  of 
comparatively  slow  growth  even  in  good  soil.  These  trees  have  a  light- 
grey  bark,  lighter  in  color  than  that  of  any  other  black  walnuts.  In 
seedlings  the  bark  toward  the  base  of  the  tree  is  of  this  light-grey  color, 
prominently  striped  with  still  lighter  markings,  while  toward  the  tops 
the  bark  is  of  a  characteristic,  light,  yellowish  green.  The  seedlings 
which  we  have  raised  have  usually  produced  the  first  year  only  a  single 
stem  with  no  side  branches,  which  stem  leans  decidedly  to  one  side 
rather  than  standing  up  perpendicular  to  the  ground.  Our  trees  have 
become  rather  bushy  in  later  years  but  have  continued  with  a  single 
main  stem,  slow  growth  and  a  leaning  position.  The  foliage  is  composed 
of  leaves  with  rather  narrow  leaflets  and  a  lighter  or  more  bluish  green 
than  those  of  other  species.  The  type  is  decidedly  different  from  any- 
thing else  which  we  have  grown  and  its  seedlings  are  entirely  distinct 
from  those  of  the  Arizona  Juglans  major,  which  are  rapid-growing, 
erect,  with  dark-colored,  almost  black  bark. 

In  various  lots  of  nuts  received  from  Texas  great  variation  has  been 
found  in  respect  to  size  and  degree  of  roughness.  Some  of  the  nuts 
were  of  the  diminutive  size  and  characteristically  deep-grooved  type 
described  above,  while  others  were  larger  and  so  much  grooved  as  to 
be  indistinguishable  from  small  nuts  of  Juglans  nigra.     So  far  as  we 


150  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

have  raised  trees  from  any  of  these  nuts,  however,  they  have  all  been 
quite  characteristic  of  the  rupestris  type  described  above.  The  range  of 
Juglans  nigra  extends  westward  into  Texas  so  that  it  would  not  be  sur- 
prising to  find  hybrids  and  peculiar  forms  there,  if  the  various  species 
hybridize  as  readily  in  that  locality  as  they  do  in  California.  Mr.  G.  A. 
Sehattenberg,  of  Boerne,  Texas,  writes  as  follows: 

"  While  I  have  not  sufficiently  investigated  the  matter,  I  have  seen 
enough  to  convince  me  that  there  are  more  than  two  very  distinct  forms 
here.  As  with  the  pecan,  hardly  two  trees  can  be  found  with  nuts  alike. 
We  collected  over  twenty-five  bushels  of  nuts  the  past  season  and  found 
hardly  two  trees  alike. " 

Mr.  F.  T.  Ramsey,  of  Austin,  Texas,  another  of  our  correspondents, 
writes  as  follows : 

"I  will  try  to  find  you  some  of  the  small  walnuts  and  mail  them. 
I  do  not  believe  that  this  particular  walnut  has  been  definitely  men- 
tioned by  any  botanist.  The  trees  rarely  have  any  top  of  any  conse- 
quence, but  are  inclined  to  throw  up  two  or  more  branches  near  the 
ground.  They  are  sometimes  nothing  better  than  a  big  bush.  In  their 
wild  state  they  are  usually  found  along  the  river  banks  and  gravelly 
streams  in  the  limestone  country  running  west  from  Austin.  Lam- 
passas  is  70  miles  from  here,  yet  the  nuts  up  there  seem  to  be  five  or 
six  times  as  large  as  the  nuts  here.  However,  some  trees  here  bear 
larger  nuts.  There  is  infinite  variation  in  the  shape  and  size  of  both 
nuts  and  trees,  also  in  the  time  of  ripening,  which  varies  from  the 
first  of  August  to  November.  Irrigation  and  good  cultivation  makes 
them  no  larger.  They  are  enormous  bearers  of  pollen.  There  are  a 
few  eastern  black  walnuts  growing  through  this  country.  Upon  the 
steep  sides  and  valleys  of  our  rough  rocky  cedar  mountains  we  have 
a  walnut  that  makes  a  large  tree,  but  bears  a  nut  in  size  just  between 
the  rupestris  and  the  black.  The  intermedia  has  a  light  green  leaf  free 
from  yellow  tinge  and  grows  slower  than  rupestris." 


NATIVE  WALNUTS  OF  NEW  MEXICO. 

Through  correspondence  we  have  obtained  some  information  as  to 
native  walnuts  in  New  Mexico,  and  also  have  planted  a  considerable 
number  of  nuts  from  that  State.  Professor  E.  0.  Wooton,  of  the  New 
Mexico  College  of  Agriculture,  writes  as  follows:  "I  am  sending  you 
specimens  of  two  kinds  of  black  walnuts  obtained  from  this  region. 
Both  kinds  are  obtained  from  relatively  large  trees  which  grow  in  the 
Mogollon  mountain  region  of  this  territory.  Neither  is  Juglans  rupes- 
tris; just  what  they  may  be  I  am  unable  to  say.  I  have  seen  Juglans 
rupestris  growing  and  know  to  a  certainty  that  the  trees  from  which 
these  nuts  came  are  not  of  that  species." 


Bulletin   231]  WALNUT    CULTURE    IN    CALIFORNIA.  151 

Mr.  James  K.  Metcalfe,  of  Silver  City,  New  Mexico,  from  whom  we 
obtained  large  and  small  types  of  walnuts,  native  to  his  locality,  writes: 
"We  have  always  considered  that  trees  which  bear  the  larger  nuts  are 
simply  those  which  grow  nearer  water."  Subsequent  to  Mr.  Metcalfe's 
death,  his  daughter,  Miss  Mary  Metcalfe,  writes:  "The  trees  grow  to 
fair  size  and  then  are  invariably  hollow.  They  are  beautiful  landscape 
trees.  30  to  35  feet  in  height,  diameter  2|  feet  or  a  little  more.  Grow 
best  where  they  can  get  down  to  water." 

These  New  Mexico  walnuts  vary  largely  in  size  and  roughness  sim- 
ilarly to  those  from  Texas.  All  the  trees  which  we  have  grown  from 
them  have  been  of  the  rupestris  type  with  light-grey  bark,  but  varying 
considerably  in  size  and  rapidity  of  growth.  Some  of  them  appear  at 
present  as  though  they  might  make  trees  of  considerable  size,  while 
others  bid  fair  to  remain  quite  small  like  typical  rupestris.  We  have 
received  nothing  from  either  Texas  or  New  Mexico  which  at  all  resem- 
bles the  typical  Juglans  major  received  from  western  Arizona.  There 
is  a  tree  in  the  Botanical  Gardens  at  Berkeley,  on  the  east  side  of  the 
walk  running  across  the  upper  end  of  the  garden  to  the  Mechanics ' 
Building,  which  was  formerly  labeled  Juglans  rupestris,  and  which 
appears  to  be  typical  of  this  species  as  we  have  grown  it  in  the  nurs- 
ery. This  tree  has  a  single  trunk  and  axis,  but  is  of  small  size  and 
slow  growth,  with  the  typical  light-grey  bark,  light-colored  foliage  and 
leaning  position. 


OTHER  AMERICAN  SPECIES. 

THE  BUTTERNUT. 

(Juglans  cinerea). 

This  well  known  native  nut  of  the  Northeastern  United  States  is 
not  native  to  California,  although  a  number  of  specimen  trees  are  to 
be  found  in  the  State,  especially  on  some  of  the  older  ranches.  There 
are  trees  in  bearing  on  the  John  Wolfskill  ranch  at  Winters,  Matthew 
Wolfskill's  in  Suisun  Valley,  George  Payne  has  a  tree  near  San  Jose, 
and  there  is  one  in  Berkeley  on  Allston  Way,  just  across  from  the 
University  cottages,  on  the  lot  which  corners  on  the  west  side  of  Oxford 
street.  This  species  is  easily  identified  by  its  long  pointed  nuts,  the 
surface  of  which  is  covered  with  high,  rough,  sharp  ridges.  It  is  a 
tree  of  slow  growth  and  of  no  economic  importance  in  California. 


152  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

FOREIGN  WALNUT  SPECIES. 

There  is.  as  stated  in  our  quotation  from  Professor  Sargent's  work 
on  page  171,  a  considerable  number  of  native  walnut  species  in  various 
parts  of  the  world.  Of  these,  the  following  are  of  some  importance  in 
California : 

Juglans  sieboldiana  Maxim. — This  forms  a  good  sized  tree,  bearing 
nuts  in  long  clusters  or  racemes  with  sometimes  as  many  as  twenty 
in  a  cluster.  The  nuts  are  very  hard  shelled,  rather  long  and  pointed, 
with  a  fairly  smooth  surface.  The  best  and  oldest  specimen  of  this 
tree  in  California  is  one  at  the  Tower  House  in  Shasta  County,  on  the 
road  between  Redding  and  Weaverville.  This  tree  was  planted  about 
I860,  and  is  now  a  large,  fine  specimen,  bearing  heavy  crops  of  nuts 
every  year.  Another  bearing  tree  may  be  seen  on  the  grounds  of  the 
old  Experiment  Station  near  Pomona,  and  there  are  probably  others 
in  the  State.  The  species  is  a  native  of  the  mountains  of  northern 
Japan  and  is  hardy,  vigorous  and  of  rapid  growth.  It  is  at  present 
of  no  economic  importance  in  this  State. 

Juglans  cordiformis  Maxim. — A  Japanese  species  considerably  like  the 
last,  trees  of  which  are  sometimes  offered  by  nurserymen.  There  appears 
to  be  some  doubt  whether  this  is  more  than  a  variety  of  Juglans  siebol- 
diana, differing  in  the  shape  of  the  nut,  which  is  heart-shaped,  flattened 
and  pointed  at  one  end,  with  a  shallow  groove  in  the  middle  of  the  flat 
sides. 

Juglans  mandshurica. — A  species  sometimes  offered  by  nurserymen, 
originating  in  Manchuria.  Said  by  some  to  be  simply  a  variety  of  the 
English  walnut. 

Juglans  boliviensis. — A  species  supposedly  native  of  Bolivia,  which  is 
said  to  form  forests  of  fine,  large,  vigorous  growing  trees  in  that  country. 
This  form  has  been  secured  by  Mr.  Frank  A.  Leib,  of  San  Jose,  from 
whom  we  have  received  scions  and  produced  young  trees  of  this  species. 

Pterocarya  caucasica. — We  have  obtained  scions  of  this  species,  which 
is  supposed  to  be  the  Caucasian  walnut  of  commerce,  from  Mr.  George 
Payne,  of  San  Jose,  who  raised  trees  from  seed.  The  seed  is  very  small 
and  not  at  all  like  that  of  ordinary  walnuts. 

HYBRID  WALNUTS. 

The  readiness  with  which  different  species  of  Juglans  hybridize  or 
cross  with  one  another  is  quite  remarkable.  To  such  an  extent  does 
crossing  of  this  sort  take  place  in  California  wherever  two  species  grow 
anywhere  near  each  other,  that  hybrid  trees  are  extremely  common  in 
every  part  of  the  State  under  such  conditions.  In  the  vicinity  of  most 
of  the  northern  towns,  like  San  Jose,  Stockton,  Santa  Rosa,  Napa,  Yaca- 


Bulletin  231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


153 


Fig.  13. — Nuts  of  hybrid  walnuts,  each  from  a  different  tree.  Natural  size. 
Royal  in  left-hand  row,  Paradox  in  right-hand  row.  Second  nut  from 
bottom  in  left-hand  row  is  Burbank  Royal. 


154  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

ville,  Winters,  Chico,  and  almost  all  the  other  towns  of  this  portion  of 
the  State,  the  northern  California  black  walnut  and  the  eastern  black, 
Juglans  nigra,  have  been  very  commonly  planted  during  the  last  sixty 
years.  The  original  specimens  of  nigra  came  from  nuts  brought  from 
the  East  and  Middle  West,  and  such  trees  are  typical  in  every  way  of 
their  species.  Among  the  younger  trees,  however,  of  later  generations 
which  grew  from  nuts  obtained  from  these  eastern  and  California  trees 
growing  more  or  less  near  together,  numerous  hybrids  may  be  found,  and 
indeed  after  two  or  three  generations  in  California  it  is  almost  impossible 
to  find  a  true  type  of  Juglans  nigra. 

Another  very  common  cross  is  that  between  various  species  of  black 
walnut  and  the  English  walnut,  which  cross  with  great  frequency  in 
California  wherever  the  species  grow  at  all  close  together.  These  two 
crosses,  that  of  California  black  on  eastern  black  and  California  black  on 
English,  received  considerable  prominence  several  years  ago  through  the 
introduction  by  Luther  Burbank  of  trees  of  these  two  types,  to  which  he 
gave  the  names  respectively  of  Royal  and  Paradox.  These  names,  in  the 
absence  of  any  others,  have  been  quite  generally  taken  up  in  California 
to  designate  trees  resulting  from  crosses  of  this  sort,  so  that  now  by  the 
name  Paradox  is  generally  understood  any  hybrid  tree  resulting  from  a 
cross  between  English  and  black  walnuts,  while  Royal  means  popularly 
any  hybrid  resulting  from  a  cross  between  two  different  species  of  black 
walnut.  Trees  of  both  of  these  crosses,  and  all  sorts  of  mixtures  and 
degrees  between  four  or  five  different  species  of  Juglans,  are  not  uncom- 
mon in  the  State,  and  the  particular  strains  introduced  by  Mr.  Burbank 
are  simply  two  very  good  examples  of  hybrids  which  have  likewise 
originated  spontaneously  in  various  parts  of  the  State. 

That  these  trees  are  true  hybrids  and  not  simply  variations  due  to 
environment  or  other  factors  is  evidenced  in  many  ways,  as  may  be  seen 
in  the  following  discussion. 

PARADOX  HYBRIDS. 

If  the  nuts  from  a  black  walnut  tree  of  any  species  which  stands  near 
an  English  walnut  tree  or  grove  be  planted,  the  resulting  seedlings  are 
apt  to  show  a  varying  percentage  of  individuals  of  decidedly  different 
appearance  from  those  of  the  black  walnut.  This  difference  consists  in 
a  more  or  less  marked  resemblance  to  English  walnut  seedlings,  the 
trees  having  bark  and  leaves  much  resembling  those  of  the  English  wal- 
nut, and,  in  general,  a  very  similar  aspect  to  the  latter  species.  In  their 
first  year  these  seedlings  may  or  may  not  differ  decidedly  in  rate  of 
growth  from  the  straight  black  walnut  seedlings,  but  after  the  first  year 
in  almost  every  case  they  show  a  more  rapid  development  and  within  the 
first  four  or  five  years  they  assume  a  size  and  rapidity  of  growth  several 


Bulletin   231]  WALNUT    CULTURE    IN    CALIFORNIA.  155 

times  as  great  as  that  of  the  other  seedlings.  The  rapid  growth  of  some 
of  these  hybrid  trees  is  truly  astonishing.  To  such  a  tree  which  he 
obtained  in  Santa  Rosa  Mr.  Burbank  gave  the  name  Paradox,  and,  as 
we  have  said,  similar  types  are  of  common  occurrence  in  almost  every 
lot  of  black  seedlings  originating  from  a  tree  near  which  an  English 
walnut  stands. 

The  cross  takes  place  just  as  freely  in  the  opposite  direction,  so  that  if 
the  nuts  from  the  English  walnut  tree  be  planted,  hybrids  are  likewise 
present  among  the  seedlings  from  such  nuts.  In  this  case,  however,  it  is 
much  more  difficult  to  distinguish  the  hybrids  from  the  true  English 
seedlings,  inasmuch  as  there  is  much  less  difference  in  their  appearance, 
particularly  during  the  first  year.  In  after  years  the  hybrids  begin  to 
outstrip  the  others  in  rapidity  of  growth  and  differ  from  them  in  their 
general  appearance.  Such  trees  are  sometimes  found  in  seedling  walnut 
groves,  and  become  very  conspicuous  by  their  great  size  as  compared  with 
the  other  trees  of  the  grove. 

There  is  no  noticeable  difference  in  appearance  between  Paradox  trees 
grown  from  black  walnuts  and  those  grown  from  English  walnuts. 
Such  trees  are  very  slow  in  coming  into  bearing  and  in  the  majority  of 
instances  are  always  very  light  producers  of  nuts.  Many  of  the  trees 
bear  enormous  crops  of  catkins  and  pollen  and  many  of  them  also  pro- 
duce very  numerous  pistillate  blossoms,  but  for  some  reason  the  latter  do 
not  seem  to  pollenize  readily  and  very  few  nuts  result.  The  nuts  vary 
considerably  in  different  trees,  but  all  that  we  have  ever  seen  are  inter- 
mediate in  form  between  the  black  and  English  walnuts,  extremely  hard 
shelled  and  of  no  value  whatever  for  eating  purposes.  There  are  a  few 
Paradox  trees  in  the  State  which  some  years  bear  quite  abundant  crops 
of  nuts,  but  these  in  every  case  stand  in  close  proximity  to  English  wal- 
nut trees,  and  it  is  possible  that  most  of  their  nuts  are  pollenized  by 
pollen  from  the  other  trees.  In  the  majority  of  instances,  even  though 
the  hybrid  trees  stand  in  the  midst  of  walnut  groves  where  they  were 
planted  for  English  walnut  trees  and  bloom  at  about  the  same  time  as  the 
other  trees,  they  set  very  few  nuts. 

The  extent  to  which  crossing  takes  place  between  the  English  walnut 
and  various  black  walnut  species  varies  with  the  nearness  of  the  trees  to 
one  another  and  also,  in  a  general  way,  with  the  degree  to  which  the 
blooming  time  of  the  trees  coincides.  The  percentage  of  hybrids  from 
certain  trees,  however,  varies  decidedly  in  different  seasons.  Some  years 
the  nuts  from  a  certain  black  walnut  tree  which  stands  near  English 
walnuts  will  give  almost  all  hybrids,  while  in  other  years  the  seedlings 
from  the  same  tree  will  be  almost  all  straight  blacks.  This  difference  is 
presumably  accounted  for  by  variation  in  the  blooming  time  of  the  tree 
from  year  to  year.     Many  trees  give  commonly  as  high  as  40  or  50  per 


156  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


Fig.   14. — Paradox  hybrid  walnut  five  years  old  from  the  seed  ;  four  years  in  present 

location. 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  157 

cent  hybrids,  and  seedlings  from  certain  trees  will  some  years  run  above 
90  per  cent. 

We  have  observed  Paradox  trees  resulting  from  the  following  crosses : 

English  x  Northern  California  Black. 

English  x  Southern  California  Black. 

English  x  Juglans  nigra. 

English  x  Juglans  major. 

Also  English  x  Paradox  and  English  x  Royal. 

Trees  of  the  first  cross  mentioned  are  found  very  commonly  in  certain 
nurseries  where  the  northern  California  species  has  been  planted.  Also 
many  trees  grow  in  the  northern  part  of  the  State  among  those  which 
have  been  planted  for  northern  California  black  and  also  those  which 
have  been  planted  for  English.  The  so-called  Smith  tree  near  Elk  Grove 
is  an  example  of  the  latter.  This  particular  tree  bears  a  much  larger  nut 
than  most  Paradox  walnuts.  There  are  few  trees  of  the  cross  in  this 
direction  in  the  State,  simply  from  the  fact  that  very  few  seedling  walnut 
groves  have  been  planted  in  the  northern  part  of  California. 

Paradox  trees  grown  from  northern  black  nuts  are  very  common. 
Most  notable  is  that  called  the  Yuba  City  tree,  which  stands  in  the  town 
of  the  above  name  just  across  the  street  to  the  north  of  the  court  house. 
This  tree  is  undoubtedly  the  largest  walnut  tree  in  California,  and,  in  all 
probability,  the  largest  in  the  world.  Its  great  size  is  accounted  for  by 
its  age,  as  it  appears  to  have  been  planted  at  least  forty  years  ago  along 
with  several  neighboring  ordinary  black  walnuts  of  the  northern  Cali- 
fornia type.  Any  one  interested  in  walnuts  will  be  well  repaid  by  a  visit 
to  Yuba  City  for  the  purpose  of  seeing  this  grand  tree.  It  is  conspicuous 
long  before  reaching  the  town,  rearing  its  enormous  head  above  every 
other  object  in  the  whole  vicinity.  The  tree  bears  a  considerable  quan- 
tity of  nuts  every  year,  but  the  amount  of  the  crop  is  insignificant  in 
proportion  to  the  size  of  the  tree. 

Other  Paradox  trees  occur  in  almost  all  the  northern  California  towns 
and  may  be  distinguished  by  their  great  rapidity  of  growth,  very  thrifty 
and  vigorous  appearance,  foliage  and  general  aspect  closely  resembling 
that  of  the  English  walnut,  and  very  light  production  of  inferior,  very 
hard-shelled  nuts. 

Paradox  trees  resulting  from  the  cross  between  the  English  and  the 
southern  California  black  are  quite  frequent  in  the  south.  In  this  case 
almost  all  the  older  trees  resulted  from  the  planting  of  the  English 
walnut,  as  very  few  of  the  southern  California  black  walnuts  have  ever 
been  planted  except  in  nurseries.  In  the  latter  case  hybrids  coming 
from  the  nuts  of  the  black  walnut  are  very  common.  In  many  of  the 
seedling  walnut  orchards  of  the  southern  part  of  the  State  hybrids  of  the 
English  and  southern  black  have  occurred.     Frequently  several  trees  of 


158 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION 


this  sort  would  develop  in  one  orchard.  These  trees  soon  attract  atten- 
tion by  their  rapidity  of  growth,  great  vigor,  and  failure  to  produce  nuts. 
Many  of  them  have  been  dug  out  or  grafted  over  as  soon  as  their  true 
nature  became  apparent.  The  Killian  tree  east  of  El  Monte  was  a 
notable  example  of  this  type,  growing  in  a  seedling  grove  on  somewhat 
sandy  land,  and  one  which  had  been  considerably  neglected  during  its 
earlier  years.  Under  such  conditions  the  trees  suffered  for  water  so  that 
they  wrere  small  and  poorly  developed  for  their  age.     This  one  tree,  how- 


Fig.   15. — Two    Paradox    hybrid    walnuts    in    English    walnut    grove    south    of 

El  Monte. 


ever,  was  an  enormous,  thrifty,  vigorous  tree,  several  times  as  large  as 
any  of  the  others,  but  producing  only  a  very  few  nuts  and  these  of  no 
value.  The  tree  has  now  been  grafted  over  to  an  English  walnut  variety. 
In  another  orchard  southwest  of  El  Monte,  on  the  road  from  that  place 
to  Whittier,  may  be  seen  two  very  large  Paradox  trees  standing  in  a 
walnut  grove  upon  decidedly  wet  land,  where  the  regular  English  walnut 
trees  are  small  and  in  poor  condition.  The  Paradox  trees  are  several 
times  larger  than  the  others  and  in  a  very  thrifty,  healthy  condition. 
These  hybrid  trees,  therefore,  resist  both  drouth  and  excess  of  wrater 


Bulletin  231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


159 


much  better  than  does  the  English  walnut,  growing  vigorously  under 
extreme  conditions  of  both  sorts. 

In  onr  experimental  orchard  on  the  state  school  grounds  at  Whittier 
there  is  a  tree  of  the  southern  California  species  which  was  planted  in 
1907  along  with  the  other  trees.  This  tree  is  the  first  in  the  grove  to 
come  out  in  the  spring,  and  all  the  English  walnut  trees  immediately 
around  it  are  French  varieties,  which  do  not  come  out  for  at  least  two 
months  after  this  black  walnut  tree  is  past  its  blooming  period.     In 


Fig.   16. 


-Camulos  tree;  Paradox.      (Photo  by  Prof.  W.  T.  Clarke.) 


the  farther  end  of  the  orchard  to  the  west,  some  five  or  six  hundred 
feet  away,  there  are  several  trees  of  southern  California  English  walnut 
varieties,  some  of  which  produce  pollen  nearly  as  early  as  does  this 
black  walnut  tree.  This  tree  in  the  spring  of  1910,  when  four  years 
old  from  the  nut,  set  a  crop  of  several  hundred  nuts,  over  90  per  cent  of 
which  when  planted  the  following  year  produced  Paradox  hybrids  of 
an  extremely  vigorous  type.  In  1911  the  tree  produced  a  much  larger 
crop  of  nuts.  It  would  appear  in  this  case  that  the  crossing  with 
English  pollen,  probably  mostly  from  the  Chase  variety,  increased  the 


160  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION, 

productiveness  of  the  tree  to  a  marked  extent  as  well  as  producing  such 
a  large  proportion  of  hybrids. 

"We  will  present  but  one  other  example  of  this  cross,  namely,  the 
Camulos  tree  on  the  old  Camulos  or  Del  Valle  ranch  situated  close 
to  Camulos  station,  in  Ventura  County,  on  the  Southern  Pacific  Rail- 
road. This  tree  stands  in  a  grove  of  old  English  walnut  seedlings,  and 
evidently  resulted  from  a  chance  cross  with  wild  black  walnut  pollen 
on  the  original  tree  whose  nuts  were  used  for  growing  the  trees  for 
this  orchard.  This  is  a  very  large,  spreading  tree,  and  is  notable  in 
producing  much  larger  crops  of  nuts  than  any  other  Paradox  tree 
which  we  have  found.  This  tree,  for  some  reason,  either  on  account 
of  inherent  productiveness  or  crossing  with  the  English  walnut  trees 
about  it,  seems  to  produce  every  year  a  very  large  crop  of  nuts.  It  is 
rather  doubtful  whether  crossing  with  the  other  trees  does  take  place 
extensively,  as  these  seedlings  are  very  uniform  and  typical  second- 
generation  Paradox  trees  rather  than  showing  any  indication  of  cross- 
ing. We  had  at  one  time  great  hopes  of  this  stock  as  a  root  for  the 
English  walnut,  on  account  of  the  productiveness  of  the  tree  and  the 
fact  that  its  seedlings  are  of  a  very  uniform  type.  Unfortunately, 
however,  like  all  other  Paradox  trees  which  we  have  tried,  its  seedlings 
have  failed  to  justify  this  hope  and  do  not  impart  any  exceptional 
vigor  to  English  walnut  trees  grafted  upon  them. 

The  Strong  tree,  on  the  ranch  of  Mrs.  H.  W.  R.  Strong,  near  "Whit- 
tier,  is  a  notable  example  of  this  cross  in  the  opposite  direction,  the 
tree  having  been  planted  for  a  southern  California  black  walnut.  This 
tree  is  thought  to  have  been  planted  somewhere  about  thirty-five  years 
ago  and  was  one  of  several  supposed  southern  California  black  seed- 
lings brought  from  Orange  County.  It  closely  resembles  at  first  sight 
the  black  walnut  type,  especially  in  the  foliage,  but  at  the  same  time 
the  leaf  and  particularly  the  bark  show  the  English  cross.  The  nut 
is  very  similar  to  the  southern  California  black  walnut.  The  tree  is 
now  of  immense  size,  especially  in  the  spread  of  branches,  which  extend 
far  out  with  the  lower  ones  coming  down  and  resting  upon  the  ground. 
The  tree  is  comparatively  a  very  light  producer,  but  it  is  evident  that 
some  years  it  is  crossed  quite  freely  by  the  neighboring  English  walnut 
trees,  and  a  large  proportion  of  its  seedlings  have  the  appearance  of 
first  cross  Paradox  trees.  The  original  tree  is  apparently  a  Paradox 
which  partakes  much  more  of  the  characteristics  of  the  black  walnut 
(the  female  parent)  than  of  those  of  the  English. 

Paradox  trees  resulting  from  a  cross  of  the  English  on  the  eastern 
black  walnut,  Juglans  nigra,  are  comparatively  uncommon,  or  at  any 
rate  there  are  few  trees  in  the  State  which  can  be  traced  positively 
to  this  parentage.     On  the  old  Pleasants  ranch  in  Pleasants  Vallev. 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA. 


161 


between  Vacaville  and  Winters,  there  is  a  large  Paradox  tree  in  the 
dooryard  near  the  corral  which  is  probably  of  this  cross.  It  is  a  par- 
ticularly thrifty,  beautiful  tree,  bearing  fair  crops  of  medium-sized 
nuts  of  the  usual  Paradox  type.  In  the  vicinity  of  Goleta,  in  Santa 
Barbara  County,  there  is  a  considerable  number  of  nigra  trees  planted 
along  the  road  on  the  county  road  from  Santa  Barbara  to  Goleta. 
Intermixed  with  these  nigra  trees  are  numerous  individuals  of  the 
southern  California  black  species,  while  on  either  side  of  the  road  are 
extensive  groves  of  English  walnuts.  In  this  instance  a  general  mix- 
ing takes  place  and  among  the  seedlings  of  the  various  trees  may  be 
found  all  sorts  of  freaks  and  hybrids.  Nuts  from  the  nigra  trees  give 
a  majority  of  straight  nigra  seedlings,  some  of  the  Royal  type  (having 
crossed  with  the  California  black),  and  a  considerable  proportion  of 
strong,  lusty  individuals  of  the  Paradox  type,  as  shown  by  their  leaves 
which  closely  resemble  those  of  the  English  walnut.  Nigra  trees  come 
out  so  much  later  in  the  spring  than  most  of  our  English  walnut  trees 
that  it  is  remarkable  that  any  cross  takes  place  between  these  species. 
Apparently,  however,  the  English  pollen  either  retains  its  vitality  for 
several  weeks  or  there  are  some  very  late  catkins  which  coincide  in 
development  with  the  bloom  of  the  nigra  trees.  These  nigra  Paradox 
trees  obtained  from  the  Goleta  nuts  appear  to  be  of  an  especially 
thrifty,  vigorous,  hardy  nature. 

The  large  old  Juglans  major,  or  Arizona  black  walnut  tree,  which 
we  have  described  as  standing  on  the  Harbison  ranch  near  Vacaville, 
crosses  freely  with  English  walnuts  in  the  vicinity,  and  usually  about 
40  per  cent  of  the  seedlings  from  this  tree  are  of  the  Paradox  type. 
It  is  reasonable  to  suppose  that  the  tree  also  crosses  with  the  northern 
California  black  walnut,  many  large  specimens  of  which  stand  close 
to  this  Arizona  tree,  but  the  pure  seedlings  of  the  northern  California 
and  major  are  so  much  alike  that  we  have  not  been  able  to  distinguish 
any  hybrids  between  these  two  in  the  nursery. 

Our  experience,  so  far  as  it  goes,  seems  to  indicate  that  the  English 
walnut  and  the  Paradox  do  not  cross  very  readily,  even  though  the  trees 
stand  close  together  in  the  same  orchard.  Either  this  is  the  case  or  else 
the  resulting  seedlings  are  indistinguishable  from  those  of  the  Paradox 
fertilized  with  its  own  pollen.  Almost  all  Paradox  trees  are  very  light 
producers  and  their  seedlings  are  of  a  fairly  uniform  type,  with  no 
individuals  among  them  of  exceptional  vigor  or  differing  noticeably  in 
appearance  from  the  majority.  Only  in  the  case  of  the  Strong  tree 
above  mentioned  have  we  found  undoubted  new  crossing  with  the 
English  walnut  among  the  seedlings,  and  this  tree,  as  we  have  said, 
resembles  its  black  walnut  parent  much  more  than  the  English.  Among 
its  seedlings  there  is  always  a  large   percentage   of  undoubted   first 

4—231 


162 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


crosses,  showing  as  very  vigorous,  characteristic  trees  entirely  different 
in  appearance  from  those  of  the  ordinary  type.  Such  individuals  have^ 
all  the  vigor  of  growth  and  other  characteristics  of  first-generation 
Paradox  trees. 

With  Royal  hybrids  the  English  seems  much  more  free  to  cross  and 
when  English  and  Royal  trees  grow  near  together  the  resulting  seedlings 
are  very  much  mixed.  We  know  of  no  large  trees  which  can  be  posi- 
tively ascribed  to  this  cross,  but  have  obtained  numerous  examples  of 
them  in  the  nursery  among  the  seedlings  of  Royal  trees  which  stood 


4 


Y  t  * 


'  ->  'S  *     '■'     **  -  •*■*-■■  ;r?  v  i 


v  '-.  * ■*■ 


Fig.   17. — Young  Royal  hybrid  walnut  tree,  showing  foliage. 

close  to  English  walnuts.    Such  individuals  have  all  the  vigor  and  desir- 
able characteristics  of  the  first  cross. 

Seedlings  of  Paradox  Trees. — Paradox  walnut  trees  of  the  first  gener- 
ation, that  is,  those  of  the  first  cross  which  originated  directly  from  nuts 
cross-pollinated  by  other  species,  are  almost  without  exception  trees  of 
unusual  vigor  and  exceptional  rapidity  of  growth.  It  would  therefore 
seem  that  seedlings  from  such  trees,  grown  from  the  nuts  which  they 
produce,  would  also  be  exceptionally  vigorous  trees.  Such  is  not  the 
case,  however,  especially  as  regards  the  use  of  such  seedlings  as  root- 
stocks  for  the  English  walnut.  These  trees,  in  every  instance  which  we 
have  tried  or  known  of,  do  not  show  exceptional  vigor,  and  English  wal- 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  163 

nuts  grafted  upon  them  do  not  grow  as  well  as  a  rule  as  those  on  straight 
black  walnut  roots.  This  subject  will  be  discussed  more  fully  in  con- 
nection with  root  stocks. 


ROYAL  HYBRID  WALNUTS. 

The  name  Royal,  as  we  have  explained,  was  first  given  by  Mr.  Bur- 
bank  to  a  supposed  hybrid  between  the  northern  California  black  and 
Juglans  nigra,  the  eastern  black.  From  the  first  published  description 
of  this  variety,  however,*  it  would  appear  that  the  staminate  parent, 
supposedly  a  northern  California  black  walnut,  was  in  reality  itself  a 
Royal  hybrid,  as  the  illustration  of  the  nut  of  this  tree  shows  a  very 
rough,  small  nut  which  must  certainly  contain  more  or  less  nigra  blood. 
Such  trees  are  quite  common  about  the  streets  of  Santa  Rosa.  The  Bur- 
bank  Royal  is  presumably,  therefore,  at  least  three  quarters  nigra  and 
one  quarter  northern  California  black. 

Following  Mr.  Burbank's  naming  of  this  hybrid,  the  term  Royal  has 
come  to  be  applied  in  California  to  all  hybrids  resulting  from  crossing 
between  different  black  walnut  species.  There  are  many  of  these  trees 
in  the  State,  particularly  about  the  older  towns  like  Santa  Rosa,  San 
Jose,  Vacaville,  Winters,  Chico,  Red  Bluff  and  other  points  in  the  Sac- 
ramento Valley,  Stockton,  Santa  Barbara  and  other  places.  It  is  indeed 
difficult  to  find  in  the  State  a  straight  Juglans  nigra,  except  those 
grown  from  nuts  brought  directly  from  the  East.  It  is  rather  remark- 
able that  the  California  species  should  hybridize  so  freely  with  nigra, 
inasmuch  as  their  blooming  periods  are  quite  distinct,  the  true  nigra 
coming  out  much  later  than  any  other  black  walnut.  Such  great  varia- 
tion exists  indeed  in  these  seedlings  of  California  nigra  trees  that  in 
some  cases  it  seems  difficult  to  account  for  all  this  variation  on  the 
basis  of  hybridization.  For  example,  there  are  some  nigra  trees  in  the 
State  planted  from  nuts  which  came  from  the  East,  which  have  all  the 
charactertistics  of  the  species.  They  are  of  slow  growth,  very  late  in 
coming  out  in  the  spring,  early  in  shedding  their  foliage  in  the  fall  and 
bear  the  typical  deep-grooved,  sharp-ridged  nigra  nuts.  When  nuts 
from  these  trees  are  planted  it  often  happens  that  almost  none  of  the 
resulting  seedlings  are  of  the  true  nigra  type,  but  they  are  hybrids, 
freaks,  variations,  mutants,  or  whatever  we  may  call  them.  We  were 
at  one  time  inclined  to  the  opinion  that  such  variation  was  the  effect 
of  environment,  causing  a  breaking  up  of  the  original  species,  but 
further  study  has  brought  us  to  believe  that  these  are  really  hybrids. 
We  are  led  to  this  opinion  from  the  fact  that  the  percentage  of  these 
unusual  trees  varies  from  year  to  year  and  that  among  the  seedlings 

♦Supplement  to  New  Creations  in  Fruits  and  Flowers,  Burbank,  1898.  See  Pacific 
Rural  Press,  Feb.  5,  1898. 


164  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION 


Fig.   18. — Burbank  Royal  hybrid  walnut  tree. 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  165 

of  these  California  nigra  trees  there  are  always  some  typical  of  the 
species,  and  some  years  a  great  many.  Moreover,  the  progeny  of  certain 
trees  are  almost  all  straight  nigra  and  the  proportion  of  such  normal 
seedlings  is  in  inverse  ratio  to  the  opportunities  for  crossing  with  other 
walnut  species. 

Juglans  nigra  was  planted  quite  commonly  with  eastern  nuts  in  Cali- 
fornia in  the  very  earliest  years  of  the  American  occupation.  Thus 
there  are  many  large  trees  of  the  species  now  growing  in  the  State. 
The  trees  are  in  almost  every  instance  closely  associated  with  specimens 
of  both  California  species  and  also  more  or  less  with  the  English  walnut. 
Many  nuts  from  these  original  trees  have  been  planted,  and  again  those 
from  the  next  generation,  down  to  three  or  four  or  perhaps  more  gener- 
ations. The  result  has  been  that  about  the  older  towns  in  the  central 
and  northern  part  of  the  State,  trees  may  be  found  which  present  every 
degree  of  gradation  between  nigra  and  the  California  species  and  also 
many  trees  which  have  only  slight  resemblance  to  either,  but  might 
easily  be  classed  as  entirely  new  species  if  their  origin  was  not  known. 
It  is  hardly  worth  while  to  describe  the  individual  trees  of  this  sort, 
so  numerous  are  they  in  the  State.  In  some  cases  it  is  difficult  or  impos- 
sible to  distinguish  between  hybrids  and  true  nigra,  as  the  nuts  arid 
foliage  are  very  similar.  Most  of  them,  however,  can  be  pretty  certainly 
picked  out  on  account  of  their  unusual  vigor  of  growth,  the  fact  that 
they  come  out  earlier  and  hold  their  foliage  later  than  true  nigra, 
a  different  aspect  of  the  tree  and  foliage  which  cannot  be  definitely 
described,  and  the  fact  that  the  nuts  are  somewhat  smoother  and  vary 
in  other  ways  from  those  of  true  nigra,  although  various  trees,  of  the 
latter  species  have  nuts  of  very  different  form  and  size. 

The  Royal  hybrid  is  very  different  from  the  Paradox  in  regard  to 
productiveness,  being  in  almost  every  instance  very  precocious  and  an 
unusually  heavy  bearer  of  nuts.  The  most  productive  nut  trees  which 
we  have  ever  seen  are  some  of  these  Royal  hybrid  walnuts.  In  favor- 
able seasons  the  ground  beneath  them  will  be  covered  several  deep  with 
nuts,  while  there  are  still  so  many  on  the  tree  that  it  is  difficult  to  see 
where  there  could  have  been  room  for  those  which  are  upon  the  ground. 

The  cross  between  nigra  and  the  northern  California  species  is  com- 
monly illustrated  in  all  the  towns  above  mentioned.  The  Burbank  Royal 
is  an  unusually  fine  tree,  being  of  tall,  erect  growth,  with  a  clean,  uni- 
form trunk,  and  of  exceptionally  vigorous  and  rapid  development.  It 
is  a  heavy  bearer  of  very  large  nuts  of  a  type  more  closely  resembling 
those  of  nigra  than  those  of  the  California  species.  The  nuts,  in  fact, 
would  pass  for  a  fine  large  type  of  nigra,  but  are  smoother  than  those  of 
the  usual  type.  They  are  deeply  and  much  grooved,  but  not  ridged  to 
any  extent. 


166  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

There  are  other  hybrid  trees  of  spontaneous  origin  in  the  central  and 
northern  part  of  the  State  which  are  fully  equal  in  every  way  to  the 
Burbank  type.  These  are  too  numerous  for  individual  description.  A 
particularly  fine  one  is  the  Pleasants  tree  which  stands  close  to  the 
bridge  on  the  county  road  near  the  old  Pleasants  ranch,  between  Vaca- 
ville  and  Winters.  This  is  one  of  the  most  beautiful  walnut  trees  in 
the  State. 

Juglans  nigra  crosses  just  as  freely  with  the  southern  California  black 
walnut  or  perhaps  even  to  a  greater  extent  than  it  does  with  the  north- 
ern type,  although  this  seems  unusual  since  the  blooming  periods  of  the 
two  species  are  several  months  apart.  The  most  notable  examples  of 
southern  California  Royals  are  the  El  Molino  or  Oak  Knoll  trees,  situ- 
ated on  the  old  Kewen  or  Mayberry  ranch,  now  the  property  of  Mr. 
H.  E.  Huntington  and  his  son  Howard  Huntington,  situated  southeast 
of  Pasadena  in  the  Oak  Knoll  district.  This  place  is  well  known  on 
account  of  having  upon  it  a  picturesque  old  Spanish  mill  built  by  the 
Mission  Fathers,  from  which  the  name  El  Molino  is  derived.  In  its 
original  condition  this  place  had  two  double  rows  of  large  black  walnut 
trees,  one  extending  on  either  side  of  a  drive  from  the  home  site  toward 
the  south,  to  what  is  now  Huntington  Drive,  and  the  other  extending 
east  and  west  to  the  west  of  the  home  site  and  the  old  mill,  near  the 
present  residence  of  Mr.  Howard  Huntington.  In  going  to  Pasadena 
on  the  El  Molino  electric  car  line  the  first  mentioned  group  of  trees  is 
situated  a  few  rods  to  the  east  of  the  point  where  the  El  Molino  line 
leaves  Huntington  Drive  and  turns  in  toward  Oak  Knoll  and  the  Went- 
worth  Hotel.  The  second  group  is  found  just  to  the  east  of  the  car 
line  at  the  point  where  it  starts  up  the  hill  below  the  Wentworth  Hotel. 
Quite  a  number  of  other  trees  of  apparently  the  same  origin  and  gen- 
eration as  these  may  be  found  scattered  here  and  there  in  dooryards 
and  by  roadsides  through  Pasadena,  Alhambra,  San  Gabriel,  El  Monte, 
Covina  and  other  neighboring  localities.  These  trees  are  all  of  the  same 
general  type,  being  large,  erect,  with  clean  trunks  and  rather  rough  bark 
and  having  a  general  resemblance  to  Juglans  nigra.  It  is  evident,  how- 
ever, that  none  of  them  are  entirely  typical  of  that  species.  The  nuts 
are  all  much  smaller  and  smoother  and  quite  different  from  the  nigra 
type,  all  the  trees  come  out  much  earlier  in  the  spring  and  hold  their 
foliage  much  later  in  the  fall  than  typical  nigra  and  they  are  all  of 
much  more  rapid  growth  than  nigra. 

There  stands  on  the  Graves  place,  near  the  El  Molino  trees,  a  group  of 
real  nigra,  planted  from  eastern  nuts,  and  the  difference  is  most  pro- 
nounced between  the  trees  in  the  two  places.  Mr.  H.  H.  Mayberry, 
whose  father  was  one  of  the  early  owners  of  the  El  Molino  ranch,  writes 
as  follows  concerning  these  trees :  ''There  formerly  stood  in  front  of  the 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  167 

old  mill  building  on  the  ranch  a  very  large  eastern  black  walnut  tree 
that  was  cut  down  about  1883  or  '84  and  had  a  diameter  of  about  four 
feet.  This  tree  was,  I  believe,  bearing  when  Colonel  Kewen  bought  the 
property  from  a  Mrs.  Holt.  The  other  black  walnut  trees  were  raised 
from  seed  from  this  original  tree. ' ' 

In  the  canons  back  of  this  ranch,  and  at  no  great  distance  from  the 
mill,  there  is  still  to  be  found  a  considerable  number  of  native  trees  of 
the  southern  California  type,  so  that  presumably  such  trees  were  orig- 
inally quite  abundant  here.  It  is,  therefore,  most  reasonable  to  suppose 
that  the  various  trees  of  this  El  Molino  type  are  Royal  hybrids,  resulting 
from  a  cross  between  the  old  nigra  tree  by  the  mill  and  these  wild 
southern  California  trees.  It  is  remarkable,  however5  that  all  the  seed- 
lings grown  from  the  nuts  of  this  tree  should  have  been  hybrids,  which 
appears  to  be  the  case.  There  are  probably  at  least  fifty  of  these  seed- 
lings represented  by  the  present  large  trees  on  the  ranch  and  a  consid- 
erable number  more  scattered  about  the  surrounding  country,  and  not 
one  of  these  trees  can  in  any  possibility  be  considered  a  true  nigra.  It 
may  be  that  in  planting  these  trees  the  largest  specimens  in  the  nursery 
were  picked  out  and  in  this  way  nothing  but  hybrids  were  chosen.  Such 
a  case  is  indeed  quite  probable,  as  the  straight  nigra  seedlings  grow  only 
a  few  inches  the  first  year,  while  the  hybrid  trees  among  them  may  be 
several  feet  in  height.  Naturally  these  largest  trees  would  be  chosen  for 
permanent  planting. 

Seedlings  of  Royal  Hybrids. — The  seedlings  originating  from  first- 
generation  Royal  trees,  of  either  the  northern  or  southern  California 
type,  are  in  general  much  more  vigorous  and  retain  the  qualities  of  their 
parents  to  a  much  greater  extent  than  in  the  case  with  seedlings  of 
Paradox  trees.  In  the  second  generation,  however,  that  is,  trees  twice 
removed  from  the  original  cross,  the  exceptional  vigor  is  mostly  lost  and 
the  seedlings  become  no  better  than  or  even  inferior  to  those  of  the 
original  species.  In  other  words,  the  Royal  hybrid  seems  on  the  average 
to  retain  its  quality  of  exceptional  vigor  of  growth  one  generation  longer 
than  does  the  Paradox.  Various  individual  Royal  trees,  however,  vary 
greatly  in  their  ability  to  impart  their  characteristics  to  their  progeny. 
Only  a  very  few  of  them  give  seedlings  which  show  uniformly  a  large 
percentage  of  trees  as  good  as  the  parent.  In  the  majority  of  cases  the 
seedlings  vary  greatly  and  are  not  at  all  uniform.  Almost  always, 
however,  the  rule  above  stated  is  maintained  that  the  seedlings  of  first- 
generation  trees  are  more  vigorous  than  those  of  the  second  generation, 
even  though  the  parent  trees  may  appear  equally  vigorous.  This  is  an 
important  fact  in  obtaining  seed  for  nursery  planting  as  a  rootstock  for 
the  English  walnut.  In  fact,  it  should  be  clearly  understood  that  while 
Royal  and  Paradox  hybrid  walnut  trees  are  quite  common  in  the  State, 


168  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

these  trees  represent  all  sorts  of  relationships  and  degrees,  a  few  being 
first  crosses,  but  many  more  being  of  the  second,  third  or  even  later  gen- 
erations. Of  the  trees  tested  by  ourselves  and  by  a  few  of  the  most 
progressive  nurserymen  who  have  taken  the  trouble  to  plant  the  nuts 
from  various  trees  separately,  only  an  extremely  small  proportion  have 
shown  themselves  worthy  of  being  used  for  producing  rootstocks  for  the 
English  walnut.  To  test  such  a  tree  thoroughly  requires  several  years, 
inasmuch  as  the  nuts  must  first  be  planted  and  the  seedlings  raised  to 
grafting  age,  the  trees  then  grafted  and  kept  in  the  nursery  for  at  least 
another  year,  after  which  they  must  be  planted  out  in  various  types  of 
soil  and  their  growth  observed  for  some  time  in  comparison  with  that  of 
trees  on  other  roots.  The  majority  of  hybrid  trees  which  produce  seed- 
lings of  exceptional  vigor  among  their  progeny  do  this  in  an  extremely 
irregular  manner,  the  seedlings  being  of  all  sorts  of  sizes  and  char- 
acteristics. English  walnuts  grafted  on  such  seedlings  will  vary  corre- 
spondingly. As  we  have  previously  said,  no  Paradox  trees  have  been 
found  whose  seedlings  are  desirable  as  rootstocks,  and  of  all  the  Royal 
trees  which  have  been  tested  there  are  less  than  half  a  dozen  in  the  State 
at  present  whose  seedlings  are  known  to  be  of  sufficient  uniformity  in 
good  qualities  to  be  desirable  for  propagation.  Seedlings  of  most  Royal 
hybrids  are  really  inferior  to  those  of  the  straight  California  black 
walnut  of  either  species  for  nursery  purposes  on  account  of  their  lack  of 
uniformity.  At  least  one  nurseryman  in  the  State  is  taking  the  trouble 
to  hybridize  certain  black  walnut  trees  by  hand  in  order  to  obtain  a 
walnut  cross  which  he  considers  especially  desirable  for  the  nursery. 

One  fact  is  to  be  remembered  in  connection  with  the  progeny  of  any 
California  walnut  tree,  namely,  that  in  almost  every  instance  walnut 
trees  of  some  sort  stand  near  to  each  other,  and  cross-pollination  is  there- 
fore always  possible  and  probably  always  goes  on  in  every  instance  to  a 
greater  or  less  extent.  The  tree  therefore  which  gives  an  unusually  good 
lot  of  seedlings  might  not  do  the  same  at  all  if  it  stood  elsewhere,  removed 
from  certain  other  trees  which  stand  near  it  and  which  cross-pollinate  its 
blossoms.  It  is  therefore  also  true  that  it  may  or  may  not  always  be 
possible  to  perpetuate  a  desirable  tree  of  this  sort  even  by  grafting,  since 
when  planted  in  some  other  place  the  combination  of  cross-pollination 
which  resulted  in  the  production  of  exceptionally  good  seedlings  may  be 
entirely  lost. 

FREAK  WALNUT  TREES. 

Walnut  trees  are  quite  frequently  met  with  in  California  which,  while 
it  is  probable  that  they  are  mostly  hybrids,  present  very  peculiar  char- 
acteristics and  have  little  resemblance  to  any  known  species.  It  is  pos- 
sible that  these  may  be  partly  the  effect  of  environment  as  well  as  that 
of  hybridization.     About  the  city  of  Berkeley  there  are  a  number  of 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  169 

black  walnut  trees  which  do  not  coincide  with  any  species  known  to  the 
writer.  There  is  a  tree,  for  instance,  on  the  University  grounds  just 
north  of  the  creek  in  the  rear  of  the  old  athletic  field,  which  is  of  a 
peculiar  type.  This  is  a  tall,  clean-trunked,  vigorous  tree,  having  much 
of  the  appearance  of  a  Royal  hybrid  and  bearing  a  small  smooth  nut. 
The  origin  of  this  tree  could  not  be  ascertained.  On  the  south  side  of 
Bancroft  Way,  just  east  of  St.  Mark's  Episcopal  Church,  there  is  a  row 
of  black  walnut  trees  which  seem  peculiar  to  themselves  in  regard  to 
specific  characteristics.  There  is  another  row  of  larger  trees  on  the  west 
side  of  College  avenue,  about  midway  between  Oakland  and  Berkeley, 
in  the  Claremont  district.  All  these  street  trees  have  a  general  resem- 
blance to  one  another  and  look  as  though  they  might  possibly  be  Royal 
hybrids.  The  writer  has  never  been  able  to  obtain  any  nuts  from  them. 
It  is  possible  that  they  are  all  seedlings  from  some  one  tree. 

On  the  El  Molino  ranch,  above  mentioned,  there  may  be  found  in  the 
canon  above  the  ranch  in  the  Oak  Knoll  property  several  most  peculiar 
trees.  These  vary  in  foliage  and  general  appearance  all  the  way  from 
that  of  the  English  walnut  to  that  of  nigra  and  calif omica  and  bear 
all  sorts  of  peculiar  nuts.  Some  are  quite  large,  some  extremely  small 
like  those  of  rupestris,  some  rough,  some  smooth,  some  round,  some 
elongated  and  some  almost  square.  Mr.  Fred  Gray,  now  superintend- 
ent of  the  Lefimgwell  ranch  near  Whittier,  who  was  formerly  super- 
intendent of  the  El  Molino  ranch,  stated  that  he  planted  many  of  these 
canon  trees  by  taking  nuts  from  the  large  Royal  trees  which  we  have 
described  and  throwing  them  about  broadcast  among  the  bushes  and 
brush  in  the  canon.  There  are  also  growing  in  this  canon  several  trees 
of  Juglans  calif  omica.  There  is  a  considerable  number  of  old  English 
walnut  trees  on  the  ranch  in  the  immediate  vicinity  of  the  black  wal- 
nuts and  these  peculiar  trees  therefore  represent,  presumably,  a  gen- 
eral mixture  of  the  three  species,  nigra,  regia  and  calif  omica. 

One  tree  in  this  canon  is  especially  peculiar.  This  has  been  called 
the  pecan-walnut  tree,  under  the  assumption  that  it  might  possibly  be 
a  cross  of  the  pecan  with  nigra,  or  the  Royal  hybrid.  There  are  sev- 
eral pecan  trees  growing  close  to  the  black  walnut  trees  on  the  ranch, 
so  that  opportunity  exists  for  such  a  cross,  if  it  were  possible.  The 
tree  mentioned  stands  on  the  east  side  of  the  canon  near  its  opening, 
and  in  its  general  characteristics  might  easily  pass  for  such  a  cross. 
The  foliage  resembles  that  of  the  pecan  to  a  considerable  extent ;  the 
bark  is  fibrous,  striated  and  very  close-fitting  and  smooth  like  that  of 
the  pecan;  the  wood  has  something  of  a  pecan  appearance,  and  the 
nut  is  exactly  intermediate  in  character  between  those  of  the  pecan 
and  the  eastern  black  walnut.  The  nuts  are  of  an  elongated  oval  form, 
pointed  on  both  ends  and  deeply  grooved.     The  seedlings  of  this  tree, 


170  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

however,  give  no  reason  to  suppose  that  they  contain  any  pecan  blood. 
They  resemble  those  of  a  good  type  of  Royal  hybrid  walnut,  and  are 
very  uniform  in  appearance.  It  is,  therefore,  safe  to  assume  that  this 
tree  is  a  hybrid  between  nigra  and  calif  ornica,  but  one  which  has 
retained  more  of  the  characteristics  of  the  latter  species,  as  the  foliage 
of  this  tree  has  considerable  resemblance  to  that  of  the  pecan.  We 
have  also  found  one  or  two  other  Royal  hybrid  trees  in  the  State  which 
bear  nuts  of  an  oval  form,  pointed  at  one  or  both  ends  very  much  like 
pecans. 

Another  peculiar  freak  is  the  so-called  walnut-oak  hybrid,  which  has 
been  described  and  discussed  by  Babcock.*  These  peculiar  trees  orig- 
inated in  Orange  County  among  a  lot  of  seedlings  of  Juglans  cali- 
f ornica.  Of  the  original  trees  there  were  about  twenty  among  two 
thousand  seedlings.  The  foliage  of  these  trees  is  quite  different  from 
that  of  the  walnut  and  resembles  very  closely  that  of  a  small-leaved 
oak.  The  fruit  is  peculiar,  being  similar  externally  in  appearance  to 
that  of  Juglans  calif  ornica,  but  peculiar  in  the  structure  of  the  nut. 
The  appearance  and  general  characteristics  of  the  tree  are  sufficiently 
characteristic  to  suggest  very  strongly  that  it  might  be  a  hybrid  between 
the  walnut  and  live  oak  tree,  which  grow  in  very  close  association  in 
southern  California.  Efforts  by  Professor  Babcock  have  thus  far  failed, 
however,  to  produce  such  a  cross  by  artificial  pollination,  and  he  has 
come  to  doubt  whether  this  is  the  true  explanation  of  the  origin  of 
this  peculiar  form.  Since  the  first  lot  of  trees  of  this  kind  was  noticed 
a  few  other  similar  individuals  have  appeared  among  seedlings  of 
Juglans  calif  ornica.  It  should  have  been  said  that  nuts  of  some  of 
these  trees  are  fertile  and  produce  seedlings,  some  of  which  have  foliage 
like  the  parent,  while  others  appear  to  have  reverted  to  the  walnut  type 
of  leaf. 

The  native  American  species  of  walnut  when  grown  in  California 
certainly  present  a  unique  example  of  freedom  in  hybridization  and 
variation.  It  has  not  been  possible  in  the  present  work  to  go  into  this 
matter  from  a  technical  standpoint,  and  we  have  perhaps  already  given 
more  space  to  the  subject  than  it  deserves  in  a  publication  upon  wal- 
nut culture.  We  desire,  however,  to  record  the  status  of  the  matter 
and  call  the  attention  of  plant  breeders  and  those  interested  in  similar 
work  to  a  most  promising  field  of  investigation. 


*E.    B.    Babcock,   The   Plant  World,   Vol.    13,    No.    2,   Teratology   in  Juglans   Cali- 
f ornica — Watson.     Silva  of  California — Jepson,  p.  50,  The  Walnut  Oak  Hybrids. 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  171 

FOSSIL  WALNUT  SPECIES. 

Many  species  of  walnut  seem  to  have  existed  in  this  and  other  coun- 
tries in  prehistoric  times.  We  quote  as  follows  from  Sargent:  "The 
type  is  an  ancient  one  in  Europe,  from  which  later  it  entirely  disap- 
peared, existing  in  the  cretaceous  flora  and  abounding  with  many 
species  during  the  tertiary  epoch ;  in  North  America  traces  of  Juglans 
appear  in  the  eocene  rocks  of  the  northern  Rocky  Mountain  region 
and  of  the  northwest  coast  from  Vancouver  Island  to  Alaska,  regions 
where  no  representative  of  the  walnut  family  now  exists,  and  in  the 
auriferous  gravel  deposit  of  the  California  Sierra  Nevada."* 


WALNUT  CULTURE  IN  CALIFORNIA. 

HISTORY. 

The  first  English  walnuts  in  California  were  probably  brought  by  the 
Mission  Fathers,  although  this  crop  does  not  seem  to  have  been  especially 
prominent  in  the  earlier  Mission  plantings ;  it  was  only  after  the  coming 
of  the  first  Americans  and  the  discovery  of  gold  that  English  walnuts 
began  to  be  extensively  planted  in  the  State,  t  The  first  trees  were  of  the 
so-called  hard-shell  type,  bearing  rather  small,  roundish  nuts,  with  a 
very  hard  shell.  There  are  still  a  few  trees  in  the  State  of  these  early 
plantings,  but  most  of  them  have  been  removed.  Such  trees  were 
planted  in  orchard  form  to  a  limited  extent  by  some  of  the  pioneers,  but 
in  its  present  form  the  walnut  industry  is  of  comparatively  recent  origin. 
Laying  aside  the  sometimes  discussed  question  as  to  whose  was  the  first 
walnut  orchard  in  California,  or  who  introduced  or  developed  certain 
types  of  nutSj  it  can  fairly  be  said  that  the  present  California  walnut 
industry  owes  its  origin  preeminently  and  fundamentally  to  the  efforts 
of  two  men :  Joseph  Sexton  of  Santa  Barbara  and  the  late  Felix  Gillet 
of  Nevada  City.  The  former  was  the  originator  and  first  propagator 
of  the  Santa  Barbara  Soft  Shell  type  of  nut,  of  which  practically  all 
the  producing  groves  of  southern  California  are  at  present  composed, 
and  the  latter  was  the  first  introducer  and  life-long  promoter  of  the 
various  French  varieties  which  form  the  basis  of  the  northern  California 
walnut  industry  as  it  exists  to-day.  A  great  many  others  have  done 
much  to  promote  the  walnut  industry  both  in  the  south  and  the  north, 
but  their  names  are  too  many  and  their  services  too  varied  to  be  men- 
tioned and  properly  estimated  here.  It  can  and  should  fairly  be  said, 
however,  that  practically  all  the  desirable  types  of  walnut  now  in  the 


♦Silva  of  North  America. 

fThe   historical   side  of  the   subject   is  well   treated  by   Lelond,    in   Rep.    Cal.    State 
Board  of  Hort.  for  1895-96. 


172 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


State  trace  back  in  their  first  introduction  either  to  Mr.  Sexton  or  to 
Mr.  Gillet,  and  that  the  few  isolated  exceptions  to  this  rule  occurred 
largely  by  chance,  and  were  not  systematically  carried  on  and  continued 
by  any  one  person. 


Fig.   19. — Joseph  Sexton,  originator  of  the  Santa  Barbara  Soft  Shell  walnut. 

The  old  fashioned  hard-shell  walnuts  were  planted  quite  commonly  in 
California  after  the  commencement  of  the  American  era,  although  not 
extensively  in  orchard  form  at  first.  The  Kellogg  orchard  near  Napa  is 
said  to  have  been  planted  in  1846  and  the  Heath  orchard  at  Carpinteria 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  173 

was  also  one  of  the  earliest  plantings.  Other  scattering  plantings  were 
made,  composed  mostly  of  dooryard  rather  than  orchard  trees,  but  it  was 
not  until  a  number  of  years  later  that  the  walnut  began  to  be  looked 
upon  as  a  commercial  crop  worthy  of  being  planted  extensively  in 
orchard  form.  The  latter  stage  of  the  industry  came  about  largely  as  a 
result  of  the  development  of  the  so-called  Santa  Barbara  Soft  Shell  nut 
by  Mr.  Sexton.  The  history  of  this  variety  has  been  given  to  the  writer 
by  Mr.  Sexton  as  follows :  In  the  spring  of  1867  he  bought  in  San  Fran- 
cisco a  sack  of  walnuts  which  came  probably  from  Chile.  These  nuts 
were  planted  that  spring  and  from  them  about  1,000  trees  were  raised, 
of  which  Mr.  Sexton  planted  about  250  himself  in  orchard  form  on  his 
place  at  Goleta.  Sixty  of  these  proved  to  be  of  the  so-called  paper-shell 
type,  the  rest  being  ordinary  hard-shells.  Only  one  of  these  250  trees  is 
still  in  existence,  this  being  a  hard-shell.  Nuts  from  these  trees,  mostly 
from  the  paper-shells,  were  planted  in  the  nursery  by  Mr.  Sexton,  and 
from  these  came  the  first  of  the  so-called  Santa  Barbara  Soft  Shell 
trees.  Of  the  first  of  these  second-generation  seedlings  sent  out  by 
Mr.  Sexton  several  groves  are  still  in  existence,  mostly  in  Santa  Barbara 
and  Ventura  counties.  The  trees  vary  considerably  in  type,  some  being 
typical  hard-shells,  some  paper-shells  and  others  of  an  intermediate  type, 
which  represents  what  may  be  called  the  typical  soft-shell.  The  latter 
type  was  considered  the  most  desirable,  the  trees  being  of  more  vigorous 
growth  and  making  greater  size  than  either  the  hard-shell  or  paper-shell, 
while  the  nuts  were  larger  than  those  of  either  of  the  other  types  and  of 
a  more  desirable  thickness  of  shell.  The  oldest  of  these  original  Santa 
Barbara  Soft  Shells  are  now  between  30  and  40  years  of  age.  Nuts 
were  again  planted  from  the  best  of  these  trees  and  soon  the  present 
walnut  industry  of  southern  California  began  its  development,  based 
almost  entirely  upon  the  type  of  nut  originated  by  Joseph  Sexton. 
Extensive  planting  began  in  Santa  Barbara,  Ventura,  Los  Angeles  and 
Orange  counties,  all  the  groves  with  practically  no  exception  being  com- 
posed of  seedling  trees  of  this  new  type.  The  industry  developed  very 
rapidly  and  under  an  enormous  demand  for  trees?  nuts  of  all  sorts  were 
planted  with  no  regard  to  selection  in  many  cases.  The  result  has  been 
that  at  the  present  time  the  Santa  Barbara  Soft  Shell  seedling  groves 
are  composed  of  a  most  heterogeneous  collection  of  trees  in  regard  to 
type  of  nut  and  bearing  qualities.  Comparatively  few  trees  of  the 
many,  many  thousands  now  in  existence  are  equal  to  the  best  of  those  in 
the  oldest  groves,  and  there  is  a  still  smaller  percentage  of  trees  superior 
to  these  oldest  ones.  The  oldest  and  best  soft-shell  trees  produce  a  fairly 
uniform  type  of  nut  and  are  all  heavy  bearers,  turning  off,  in  spite  of 
blight  and  other  vicissitudes,  more  than  300  pounds  of  nuts  per  year. 
They  are  fine,  large,  thrifty  trees,  still  in  healthy,  vigorous  condition 
wherever  planted  in  good  soil,  and  it  may  truly  be  said  that  were  the 


174 


UNIVERSITY    OF    CALIFORNIA  — EXPERIMENT    STATION. 


present  groves  composed  of  trees  of  as  gocd  average  quality  as  the  best 
of  these  oldest  trees,  the  walnut  industry  would  be  at  present  in  far 
better  condition  than  it  is. 


Fig. 


!0. — Felix  Gillet,  introducer  of  the  best  French  walnuts  into  California 
and  originator  of  most  of  the  French  seedling  varieties. 


As  plantings  and  the  number  of  bearing  trees  of  the  Santa  Barbara 
Soft  Shell  type  multiplied,  particularly  thoughtful  growers  here  and 
there  began  to  notice  the  variation  in  the  trees  and  to  consider  the  possi- 
bility of  propagating  from  the  best  of  them,  both  by  seed  and  by  grafting. 


Bulletin  231]  WALNUT   CULTURE   IN   CALIFORNIA.  175 

Many  orchards  were  planted  with  seedling  trees  derived  from  especially 
selected  nuts,  but  the  greatest  step  in  advance  was  taken  when  trees  of 
special  excellence  began  to  be  picked  out  here  and  there  and  propagated 
by  grafting  or  budding  in  the  same  manner  that  other  fruit  tree  vari- 
eties are  propagated.  Thus  originated,  for  instance,  the  Placentia  Per- 
fection, Ford's  Improved,  Disher's  Prolific,  El  Monte,  and  various  other 
varieties  of  which  the  original  trees  were  Santa  Barbara  Soft  Shell 
seedlings.  Much  difference  of  opinion  existed  at  first  as  to  the  merits 
and  qualities  of  the  grafted  tree  in  comparison  to  the  seedling,  and  there 
was  in  the  beginning  a  strong  prejudice  against  the  former  and  an  idea 
of  inherent  superiority  of  the  seedling  tree  in  thrift,  vigor  and  pro- 
ductiveness. As  time  went  on,  however,  abundant  proof  was  afforded, 
through  the  rapidly  increased  plantings  of  grafted  trees,  that  this  dif- 
ference was  entirely  imaginary  and  that  no  radical  difference  existed 
between  the  walnut  and  other  fruit  trees,  whereby  the  superior  qualities 
of  particularly  desirable  individuals  could  not  be  reproduced  and  multi- 
plied indefinitely.  Thus  at  the  present  time  the  planting  of  seedling 
trees  has  practically  ceased  and  no  well-informed  grower  would  consider 
the  planting  of  a  seedling  grove. 

In  the  northern  part  of  the  State  the  walnut  industry  has  had  quite 
a  different  development.  Trees  of  the  old  hard-shell  type  were  planted 
in  this  portion  of  the  State  as  early  as  in  the  south,  but  the  extensive 
development  of  the  industry  in  the  latter  portion  of  the  State  based  on 
the  Santa  Barbara  Soft  Shell  type  of  nut  did  not  extend  north  of 
Santa  Barbara  County.  The  pioneer  and  chief  promoter  of  walnut 
culture  in  northern  California  was  Felix  Gillet  of  Nevada  City.  Born 
in  France  in  1835,  Mr.  Gillet  came  to  this  country  in  1852,  arrived 
in  California  in  1858  and  in  1859  in  Nevada  City,  which  place 
thereafter  remained  his  home.  Mr.  Gillet  had  a  natural  interest  in 
horticulture,  and  in  1871  began  the  development  of  his  Barren  Hill 
Nursery.  He  was  particularly  interested  in  nut  culture  and  at  a  very 
early  date  began  introducing  from  France  the  best  of  the  nuts  grown 
in  that  country,  particularly  the  walnut.  From  1871  on  he  imported 
many  shipments  of  scions  and  nursery  trees,  and  was  the  first  intro- 
ducer into  California  of  practically  all  the  French  walnut  varieties 
which  we  now  have.  He  likewise  propagated  trees  of  these  varieties 
in  his  own  nursery  and  also  raised  many  seedlings  from  French  varie- 
ties with  the  idea  of  developing  new  varieties  of  special  adaptation  to 
California.  As  a  result  of  Mr.  Gillet 's  efforts  the  Franquette,  our  lead- 
ing walnut  in  the  northern  part  of  the  State,  was  established  in  Cali- 
fornia, while  from  seedlings  of  his  raising  originated  the  Concord,  San 
Jose,  and  possibly  the  Chase  varieties. 

Following  Mr.  Gillet,  further  introductions  from  France  were  made 


176  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

by  various  parties  of  the  varieties  to  which  he  had  called  attention,  and 
the  planting  of  the  best  of  these,  particularly  the  Franquette,  was  car- 
ried on  by  various  people.  Without  question,  the  chief  credit  for  the 
present  popularity  of  the  Franquette  variety  is  due  to  the  late  Mrs. 
Emily  Vrooman,  who  planted  an  extensive  grove  of  this  variety  near 
Santa  Rosa  at  a  time  when  walnut  growing  on  a  commercial  scale  in 
northern  California  was  still  considered  doubtful  or  impossible.  As 
a  result  of  the  success  of  Mrs.  Vrooman 's  grove,  others  came  to  appre- 
ciate the  possibilities  of  walnut  culture  in  the  northern  part  of  the 
State  and  the  valuable  qualities  of  the  Franquette  variety.  In  later 
years  there  has  been  a  growing  interest  in  walnut  culture  in  the  cen- 
tral and  northern  part  of  the  State,  which  has  been  shared  in  and 
assisted  by  numerous  individuals  who  cannot  be  mentioned  individ- 
ually here. 

LOCATION  FOR  WALNUTS. 

CLIMATE. 

The  limitations  of  commercial  walnut  growing  are  rather  closely 
drawn  by  climatic  conditions. 

Frost. — In  regard  to  temperature,  the  tree  is  able  to  withstand  a 
considerable  degree  of  cold  so  long  as  it  is  not  subject  to  severe  frost 
and  freezing  outside  the  period  of  dormancy,  and  also  provided  the 
trees  do  not  suffer  for  moisture  during  the  dormant  period.  English 
walnut  trees  are  not  uncommon  in  the  Atlantic  States  as  far  north  as 
New  York,  and  there  are  trees  even  in  Northwestern  New  York  which 
bear  well  every  year.  The  most  evident  effects  of  freezing  upon  the 
walnut  are  seen  in  cases  where  heavy  frosts  come  on  suddenly  in  the 
fall  while  the  trees  are  still  green  and  not  yet  in  a  dormant  condition, 
or  when  the  same  thing  occurs  in  the  spring  after  the  trees  have  com- 
menced growth.  In  the  latter  case,  even  in  southern  California,  wal- 
nut trees  are  sometimes  badly  frozen.  In  general,  it  may  be  said  that 
so  far  as  winter  temperatures  are  concerned,  the  tree  is  almost  as  hardy 
as  the  peach  or  apricot  and  will  flourish  almost  anywhere  in  California 
where  these  trees  do  well.  In  regard  to  late  spring  frosts,  it  is  for- 
tunately the  case  that  different  walnut  trees  and  varieties  vary  widely 
in  regard  to  their  time  of  coming  out  in  the  spring,  ranging  in  this 
respect  over  a  period  of  several  months.  It  is  thus  possible  in  a  locality 
subject  to  late  spring  frosts  to  select  a  late  variety  of  walnut  and  thus 
escape  the  danger  period.  It  may,  therefore,  be  said  in  respect  to  low 
temperatures  that  walnuts  can  be  grown  in  practically  all  the  culti- 
vated portions  of  California,  so  far  as  this  one  feature  is  concerned,  by 
choosing  varieties  of  the  proper  foliation  period  in  the  spring.  In  the 
central  and  northern  parts  of  the  State  there  has  been  in  general  too 


Bulletin  231]  WALNUT   CULTURE  IN   CALIFORNIA.  177 

much  fear  of  spring  frosts  in  relation  to  walnuts.  About  almost  any 
of  the  towns  in  this  portion  of  the  State  there  may  be  found  early  trees, 
which  to  all  appearances  produce  as  regularly  and  abundantly  as  those 
in  the  south.  "While  walnuts  are  sometimes  damaged  by  frost  even  in 
the  best  of  the  southern  California  districts,  the  tree  is  not  unusually 
sensitive  in  this  respect  and  even  the  earliest  of  our  walnuts  come  out 
later  than  many  of  our  ordinary  fruit  trees.  We  very  much  doubt 
whether  the  walnut  in  many  northern  California  districts  would  be 
injured  by  frost  any  more  than  the  almond,  apricot,  peach  or  grape, 
and  the  prospective  grower  need  not  absolutely  discard  all  early  vari- 
eties for  this  one  reason  alone.  It  may  further  be  said  that  during  the 
spring  of  1911  when  there  was  much  late  frost  in  the  State,  some  of 
the  latest  varieties  of  walnut  were  badly  injured,  when  earlier  varieties 
in  the  same  locality  had  reached  sufficient  development  so  that  they 
withstood  frost  with  no  injury  whatever. 

Trees  which  suffer  for  moisture  during  late  fall  and  winter  are  likely 
to  be  severely  killed  back  at  temperatures  which  otherwise  would  not 
affect  them.     See  Die  Back,  page  372. 

Heat. — The  walnut  tree  is  one  which  does  not  take  kindly  to  extreme 
summer  heat,  and  its  commercial  culture  is  limited  to  a  considerable 
extent  by  this  factor.  In  the  extremely  hot  desert  valleys  of  the  State 
the  tree  is  not  at  all  well  adapted,  becoming  injured  and  repeatedly 
killed  back  by  drying  and  burning  of  the  leaves  and  tender  shoots. 
The  idea  which  once  prevailed,  however,  that  walnut  culture  is  possi- 
ble only  in  the  immediate  vicinity  of  the  coast  has  become  considerably 
modified  in  recent  years.  Sufficient  plantings  have  been  made  to  indi- 
cate that  the  tree  flourishes  practically  all  over  the  State,  except  in 
the  very  hottest  and  driest  portions,  and  it  has  been  demonstrated  that 
nuts  can  be  produced  over  a  similar  territory.  A  serious  drawback, 
however,  is  the  burning  or  discoloration  of  the  nuts  by  the  sun  even 
in  localities  where  the  tree  flourishes  well.  Here  again  the  matter  of 
choice  of  varieties  becomes  important  since  there  is  much  variation  in 
its  susceptibility  to  sunburn.  The  most  serious  form  of  sunburn  takes 
the  form  of  an  actual  shriveling  and  blackening  on  one  side  of  the 
green  hulls  of  the  immature  nuts.  This  is  worst  on  the  nuts  which  are 
most  exposed  to  the  sun,  also  on  trees  which  are  unthrifty  or  not  in  a 
good  vigorous  condition.  Walnut  trees  or  varieties  best  adapted  to 
the  hottest  localities  are,  therefore,  those  which  have  the  most  abundant 
foliage,  in  which  the  nuts  are  borne  well  down  among  and  under  the 
leaves,  and  which  are  naturally  of  thrifty,  vigorous  growth.  Burning 
by  the  sun  is  also  less  severe  upon  trees  standing  in  good  soil  with 
plenty  of  moisture  than  upon  those  in  light  dry  soil.  A  less  prominent 
effect  of  sunburn  consists  in  a  burning  or  discoloration  of  the  thin  pel- 

5—231 


178  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

licle  which  envelopes  the  kernel  of  the  nut.  In  very  hot  places  such 
discoloration  occurs  even  without  visible  burning  of  the  outside  of  the 
husk.  This  effect,  however,  like  that  of  frost,  is  one  which  we  believe 
to  have  been  largely  overestimated.  There  is  much  difference  in  differ- 
ent trees  or  varieties  as  to  the  color  of  the  pellicle,  but  in  good,  white- 
meated  varieties  we  have  seen  nuts  of  perfect  quality  in  this  respect 
produced  in  very  hot  localities  in  the  interior  of  the  State.  Where  the 
heat  is  not  so  severe  as  to  scorch  the  foliage,  stunt  the  growth  of  the 
tree,  or  visibly  burn  the  nuts,  little  attention  need  be  paid  to  this  dis- 
coloration of  the  pellicle  so  long  as  proper  varieties  are  planted.  The 
chief  consideration  in  the  warmer  localities  should  be  to  choose  vari- 
eties of  vigorous  growth,  with  abundant  foilage,  well  shaded  nuts  and 
thick  husks. 

Hot  dry  weather  at  the  time  of  blooming  in  the  spring  is  sometimes 
as  disastrous  or  even  more  so  than  frost.  There  is  little  danger  of  this 
in  the  northern  part  of  the  State,  but  in  the  south  the  setting  of  nuts 
is  sometimes  seriously  damaged  by  conditions  of  this  sort,  and  indeed 
this  danger  is  sufficiently  great  to  make  the  planting  of  any  late  variety 
of  doubtful  advisability  in  the  south. 

Specifically,  we  may  say  in  regard  to  the  climatic  limitations  of  wal- 
nut culture  in  California  that  wherever  suitable  soil  and  water  supply 
can  be  obtained  and  by  the  proper  choice  of  varieties,  the  crop  can  be 
successfully  produced  in  all  the  counties  of  southern  California  save 
in  the  desert  portion,  in  almost  all  the  coast  counties  of  the  State,  except 
in  localities  very  much  exposed  to  cold  wind  and  fog  a  large  portion  of 
the  time,  in  all  the  valleys  about  San  Francisco  Bay  and  in  most  of  the 
country  within  200  miles  of  San  Francisco  or  even  further.  In  the 
interior  valleys  no  definite  line  can  be  drawn  where  commercial  walnut 
possibilities  cease,  as  in  these  warmer  regions  much  depends  upon  soil 
and  moisture  supply.  In  the  mountain  districts  walnuts  can  be  grown 
almost  anywhere  except  at  the  higher  altitudes  where  spring  and  sum- 
mer frosts  are  of  regular  occurrence. 

SOIL. 

A  fairly  heavy,  deep  soil  with  an  abundance  of  moisture,  though  at 
the  same  time  thoroughly  well  drained,  presents  by  far  the  best  condi- 
tion for  successful  walnut  culture.  Very  little  success  can  be  expected 
on  light  sandy  soil  subject  to  a  fluctuating  moisture  supply  and  walnut 
culture  should  not  be  attempted  under  such  conditions.  Trees  on  such 
soil  are  less  thrifty,  less  productive,  and  much  more  subject  to  all  the 
troubles  which  affect  the  walnut  in  this  State.  Walnut  trees  on  light 
soil  may  flourish  for  a  time,  especially  if  plentifully  supplied  with 
wate-  and  in  the  beginning  of  the  industry  in  this  State  it  was  thought 
that  <niM]  were  the  best  conditions  for  walnuts.     Trees  grown  in  this 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  179 

way,  however,  have  proven  to  be  short  lived  and  more  subject  to  disease, 
and  nothing-  has  been  more  positively  demonstrated  by  experience  than 
the  desirability  of  heavy  soil  for  the  walnut.  The  quality  of  the  subsoil 
is  of  particular  importance  since  the  roots  of  the  walnut  go  down  fairly 
deep.  A  strong  or  heavy  (though  not  wet  or  impervious)  subsoil  is 
absolutely  essential. 

A  uniform  and  abundant  supply  of  soil  moisture  is  necessary,  although 
the  tree  is  considerably  resistant  to  drouth,  especially  when  grown  on 
proper  roots.  Walnuts  are  frequently  grown  in  California  without  irri- 
gation even  in  the  southern  part  of  the  State,  but  unless  planted  upon 
soil  of  exceptionally  good  water-retaining  capacity  more  or  less  irriga- 
tion is  almost  always  beneficial  and  profitable.  In  many  cases  where  the 
trees  survive  and  do  fairly  wrell  without  water  they  would  grow  much 
more  rapidly,  come  into  bearing  sooner  and  bear  much  larger  crops  if 
supplied  with  water.  Too  great  an  amount  of  moisture  in  the  soil  with 
water  constantly  standing  near  the  surface  is  very  unfavorable  to  wal- 
nut culture  and  the  trees  will  not  long  withstand  conditions  of  this  sort. 
Some  latitude  can  be  obtained  in  this  respect  by  the  use  of  a  root  best 
adapted  to  excessive  moisture,  but  it  is  hazardous  to  attempt  walnut 
culture  on  land  where  the  water  level  stands  within  less  than  eight  feet 
of  the  surface  or  where  it  is  likely  to  rise  after  the  trees  are  planted. 

DISTANCE  OF  PLANTING. 

In  practically  all  the  old^r  walnut  groves  in  the  State  the  trees  were 
planted  too  near  together.  The  walnut  tree  is  one  which  continues 
growth  for  many  years,  making  a  large,  spreading  top,  so  that  the  trees 
very  soon  come  together  unless  planted  a  long  distance  apart.  Further- 
more, the  production  of  nuts  seems  to  be  particularly  favored  by  exposure 
to  the  light  and  open  air  on  all  sides  of  the  tree.  The  mistake  of  plant- 
ing the  trees  too  close  together  should  therefore  be  carefully  guarded 
against.  "With  vigorous  growing  varieties  on  good  soil  60  feet  apart  is 
none  too  much,  and  less  than  50  feet  should  not  be  considered  in  any 
case.  Sixty  by  sixty  feet  gives  about  12  trees  per  acre,  50  by  50,  17 
trees  per  acre  and  40  by  40,  27  trees  per  acre,  when  planted  in  squares. 
By  alternating  the  rows  these  numbers  are  slightly  increased. 

Inter  planting. — With  trees  planted  at  these  wi'le  intervals  and  also 
somewhat  slow  in  coming  into  bearing  as  compared  with  many  fruit 
trees,  it  becomes  quite  desirable  when  planting  walnuts  to  interplant 
with  some  other  tree  or  crop  in  order  to  get  something  off  the  land  while 
the  walnuts  are  coming  into  bearing.  Fortunately,  this  is  not  especially 
objectionable,  as  the  walnut  is  a  deep  rooting  tree,  and,  if  properly 
treated,  shows  no  injurious  effects  from  judicious  interplanting.  In 
some  cases  interplanting  or  double  planting  with  walnuts  is  practiced, 


180  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

either  with  the  same  variety  as  that  of  the  permanent  planting,  or  with 
another  more  precocious,  though  ultimately  less  desirable,  variety. 
Such  interplanting  with  walnuts  may  be  done  either  in  one  or  both  direc- 
tions, so  that  there  may  be  two,  three,  or  four  times  as  many  trees  per 


01010 


01010 


0  10  10 


0  10  10 


Diagram,  showing  method  of  quadruple-planting  of  walnuts  in  squares,  (^perma- 
nent trees,  60  feet  apart.  1=trees  for  first  cutting  out.  2=second  cutting.  3=third 
cutting. 

acre  as  will  remain  permanently,  according  to  the  extent  to  which  the 
interplanting  is  done.  The  only  objection  to  such  interplanting  as  this 
lies  in  the  reluctance  of  the  average  man  to  cut  out  the  temporary  trees 


Bulletin  231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


181 


when  the  proper  time  arrives.  So  weak  has  human  nature  proven 
itself  in  every  instance  of  such  interplanting  with  which  we  are  familiar 
that  we  hesitate  in  recommending  this  method.     The  trees  grow  rapidly 


■  i  i 

\                 £.         ^          JyjfiSr'  Li 

^■fflti  • 

1  **'"'■"          f**_ 

#1  .-»■   ,*'              «KnK*M 

3 

-  ora  3Wflh3^rjP"B*K '  '"w 

^U^^^^^^^^^me^sS^k 

ww9K^BS^^fSSS^^^^^^Sit^^^^SB^St 

ggH  BSPgp^  ^bj^^Sct? 

JoK'SK 

l*r  ■                     *JLi.  &J"             .^«1hBesI 

^™^HJm   ^ir 

:IP^B^W^~ 

^RBNBSgk' 

•vv&i 

jjjBj^'TftiHB 

. 

jy^Mg^ 

Fig.   21. — Top — Interplanting  with  peaches.     Center — Grapes.     Bottom — Grove  started 

by  planting  nuts  in  place. 

and  for  proper  results  must  be  ruthlessly  slaughtered  just  as  they  are 
coming  into  their  prime.     Unless  one  is  fully  prepared  to  carry  out  such 


182  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

a  slaughter,  however,  just  as  soon  as  the  tops  begin  to  reach  out  and 
touch  each  other,  he  should  not  consider  interplanting  with  walnuts.  If 
double  planting  is  practiced  in  both  directions,  using  four  times  the 
number  of  permanent  trees  per  acre,  the  cutting  may  be  extended  over 
at  least  three  years,  taking  out  one  fourth  of  the  trees  each  year.  Inter- 
planting is  frequently  done  with  peaches,  apricots,  grapes,  berries  and 
other  quick-maturing  fruits,  also  with  all  sorts  of  vegetables  and  annual 
crops.  There  is  no  objection  to  any  of  these,  so  long  as  the  walnut 
trees  are  protected  from  injury  and  do  not  suffer  for  moisture.  The 
latter  is  one  of  the  greatest  dangers  and  should  be  carefully  guarded 
against.  Interplanting  with  alfalfa  is  a  common  practice  and  a  very 
desirable  one  if  the  alfalfa  does  not  rob  the  walnut  trees  of  moisture. 
The  latter,  however,  is  frequently  the  case.  In  order  to  guard  against 
this,  the  walnuts  should  not  depend  for  irrigation  upon  the  water 
which  they  get  along  with  the  irrigation  of  the  alfalfa.  A  cultivated 
strip  should  be  maintained  on  each  side  of  the  walnut  rows  and  water 
should  be  run  in  separate  furrows  for  the  irrigation  of  the  trees. 

CULTURE. 

SOIL  HANDLING. 

The  various  operations  of  stirring  the  soil,  such  as  plowing  and  culti- 
vating, do  not  appear  to  be  of  as  much  importance  in  walnut  culture  as 
in  the  case  of  some  other  trees.  In  relation  to  the  conservation  of  soil 
moisture  cultivation  has  its  importance,  particularly  where  the  water 
supply  is  somewhat  limited,  but  given  plenty  of  moisture  and  suitable 
soil  the  walnjut  tree  is  one  which  seems  to  flourish  and  produce  satisfac- 
tory crops  whether  the  ground  be  thoroughly  cultivated  or  not.  It  is, 
indeed,  a  matter  of  common  observation  to  see  large,  thrifty  walnut  trees 
producing  the  best  of  crops  while  standing  in  the  hard-packed  soil  of  the 
dooryard  or  roadside  with  no  cultivation  whatever.  In  fact,  trees  in 
such  situations  seem  sometimes  to  flourish  actually  better  than  those  in 
neighboring  orchards  where  some  degree  of  cultivation  is  practiced. 
Many  growers  call  attention  to  trees  standing  in  the  dooryard  or  about 
the  buildings  where  they  receive  no  cultivation  and  little  or  no  irriga- 
tion, which  are  noticeably  in  better  condition  and  more  productive  than 
trees  near  by  planted  in  orchard  form.  The  superiority  of  such  trees 
is  not  due,  however,  to  their  lack  of  irrigation  and  cultivation,  but  rests 
largely  upon  the  fact  that  being  planted  away  from  other  trees  they 
have  better  exposure  to  the  light  and  air  than  trees  in  the  orchard, 
which  appears  to  be  a  very  essential  factor  with  the  walnut.  Again,  it 
is  true  that  walnut  trees,  if  they  stand  in  fairly  good  soil,  actually  do 
better  without  any  cultivation  than  they  do  if  the  ground  is  plowed  or 
cultivated  occasionally  in  a  superficial,  unsystematic  manner.     The  tree 


Bulletin-  231]  WALNUT    CULTURE   IN    CALIFORNIA.  183 

apparently  retains  much  of  the  nature  of  a  forest  tree  in  this  respect  and 
does  better  when  left  to  itself  with  the  soil  undisturbed  than  when  the 
soil  is  cultivated  in  the  above-described  irregular  manner.  This  by  no 
means  goes  to  prove,  however,  that  good  cultivation  is  injurious  or 
unnecessary  in  walnut  culture,  for  experience  has  shown  this  to  be  far 
from  the  case.  Especially  in  regions  where  the  rainfall  is  limited  and 
the  dry  season  long  and  hot,  regular,  thorough  cultivation  is  as  beneficial 
and  profitable  in  the  walnut  orchard  as  with  citrus  or  other  trees.  In 
regions  with  more  abundant  rainfall  and  less  severe  dry  seasons  cultiva- 
tion is  not  so  essential ;  the  chief  consideration  in  all  cases  is  that  of  the 
conservation  of  soil  moisture.  The  latter  must  be  maintained,  but 
whether  by  irrigation  or  cultivation  matters  little.  If  the  soil  is  suffi- 
ciently moist  cultivation  is  not  as  essential  with  the  walnut  as  with  many 
other  fruit  trees. 

In  practice  it  is  customary  to  plow  the  grove  once  a  year  during  the 
spring,  followed  by  harrowing  and  cultivation  to  put  the  soil  into  good 
mechanical  condition.  After  this,  the  ground  is  usually  cultivated 
occasionally  during  the  summer,  at  least  after  each  irrigation  if  this  be 
practiced,  in  order  to  keep  it  from  baking,  keep  down  the  weeds  and 
hold  the  moisture.  A  number  of  growers  in  southern  California  have 
tried  in  recent  years  the  experiment  of  carrying  on  their  walnut  groves 
with  no  plowing  or  cultivation  whatever,  but  with  abundant  irrigation. 
In  some  cases  permanent  irrigation  furrows  have  been  made  between  the 
trees,  while  in  others  the  water  is  simply  turned  into  the  orchard  and 
allowed  to  flood  the  whole  ground  as  thoroughly  as  possible.  The  weeds 
and  grass  have  been  allowed  to  grow  up  or  pastured  off  with  horses  and 
cattle.  Under  such  treatment  an  actual  improvement  has  been  mani- 
fest in  the  condition  of  some  walnut  groves.  Whether  such  improve- 
ment, however,  is  due  to  the  lack  of  cultivation  we  are  inclined  to  doubt, 
but  would  rather  attribute  it  to  the  increased  water  supply  which  the 
trees  have  received.  Such  experiments  have  strengthened  the  opinion, 
however,  that  cultivation  is  not  particularly  essential  with  the  walnut  so 
long  as  it  receives  plenty  of  moisture.  In  cases  where  walnuts  are 
grown  without  irrigation  there  can  be  no  question  that  thorough,  syste- 
matic cultivation  during  the  summer  season  will  assist  in  holding  the 
moisture  of  the  soil.  That  many  trees  grow  and  flourish  without  such 
cultivation  and  without  irrigation  is  again  no  indication  of  beneficial 
effects  of  non-irrigation,  but  simply  shows  that  in  these  particular  local- 
ities sufficient  soil  moisture  is  present  without  any  special  efforts  toward 
its  conservation. 

IRRIGATION. 

The  walnut  tree,  while  not  dependent  upon  constant  irrigation  like  the 
orange  and  many  other  more  shallow-rooted  trees,  is  at  the  same  time  a 
large  consumer  of  water  and  needs  plenty  of  moisture  for  successful 


184  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

development.  The  majority  of  the  trees  in  the  northern  part  of  the 
State  are  grown  without  irrigation,  and  even  in  the  southern  part  many 
groves  receive  little  or  no  water  in  addition  to  the  natural  rainfall.  In 
seasons  of  abundant  precipitation  trees  under  such  conditions  get  along 
very  well,  and  it  may  be  said  that  the  walnut  is  as  well  adapted  as  almost 
any  of  our  ordinary  fruit  trees  to  grow  without  irrigation.  There  are 
localities,  especially  in  the  northern  part  of  the  State,  where  the  crop 
can  be  produced  successfully  and  regularly  without  irrigation.  Further- 
more, there  is  considerable  variation  in  the  moisture-gathering  ability  of 
the  various  kinds  of  root  upon  which  the  tree  may  be  grown  so  that  by 
proper  choice  in  this  respect  much  may  be  done  to  make  walnut  growing 
possible  on  non-irrigated  lands.  In  general,  however,  it  is  true  of  wal- 
nut growing,  as  with  all  other  fruit  growing  in  California,  that  no  one 
factor  is  as  desirable  or  useful  as  the  possibility  of  an  abundant  and 
regular  water  supply.  Even  though  the  trees  may  be  able  to  live  with- 
out irrigation  and  may  grow  quite  well  and  produce  good  crops  during 
most  seasons,  it  is  still  true  that  even  as  a  matter  of  insurance  against 
dry  years  a  possible  water  supply  is  extremely  valuable.  Furthermore, 
there  is  no  spot  in  the  State  so  favored  with  natural  soil  moisture  but 
that  with  irrigation  during  the  first  few  years  the  trees  would  grow  much 
faster,  come  into  bearing  earlier,  and  produce  more  satisfactory  returns 
to  the  owner. 

By  this,  however,  we  do  not  intend  to  discourage  the  planting  of  wal- 
nuts on  non-irrigated  lands.  The  tree  is,  as  we  have  said,  as  well  adapted 
to  such  conditions  as  any  other  fruit  tree,  and,  indeed,  may  be  grown 
more  successfully  without  irrigation  than  most  other  fruits  if  grown 
upon  a  proper  root. 

As  to  the  particular  methods  of  irrigation  practiced  with  the  walnut, 
it  may  be  said  that  the  tree  is  most  likely  to  suffer  from  lack  of  moisture 
during  the  fall  and  winter  after  the  crop  of  one  season  is  off  and  before 
that  of  the  next  year  has  started  to  develop.  Quite  frequently  it  is  the 
case  that  the  fall  rains  are  late  in  commencing  and  the  walnut  tree  is 
especially  likely  to  suffer  from  such  a  condition.  Although  it  may  not 
be  in  active  growth  and  practically  dormant,  a  lack  of  moisture  at  this 
times  dries  out  the  branches,  twigs  and  buds,  lowers  the  vitality  of  the 
tree,  impairs  its  vigor  for  the  following  season,  makes  it  more  susceptible 
to  injury  by  cold,  and  is  in  many  other  ways  injurious  and  disastrous. 
For  this  reason  it  is  coming  to  be  more  and  more  the  practice  among 
the  best  walnut  growers  to  irrigate  heavily  during  the  fall  and  winter, 
supplementary  to  the  winter  rains  and  creating  a  storehouse  of  moisture 
in  the  soil  for  the  summer.  If  the  subsoil  is  thoroughly  soaked  down 
and  not  allowed  to  become  dried  out  during  the  fall  and  winter,  the 
tree,  on  fairly  heavy  soil  at  least,  is  much  less  dependent  upon  sum- 
mer  irrigation  than  is  the   case  with  citrus  and  many  other   trees. 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  185 

During  the  summer  it  is  ordinarily  desirable  to  irrigate  at  least  once 
or  twice,  especially  toward  the  time  of  maturity  of  the  crop,  in  order 
that  the  nuts  may  have  plenty  of  moisture  for  their  proper  develop- 
ment. Walnut  irrigation  therefore  resolves  itself  very  largely  into, 
first,  guarding  against  drying  out  of  the  soil  during  the  fall  with  irri- 
gation at  this  time  if  necessary  to  accomplish  such  a  result ;  second, 
copious  irrigation  during  the  latter  part  of  the  winter,  unless  the  rains 
have  been  sufficient  to  thoroughly  saturate  the  subsoil  down  to  the 
depth  of  the  lowest  roots ;  third,  at  least  one  irrigation  during  the  sum- 
mer, usually  in  August,  when  the  nuts  are  approaching  maturity. 
When  interplanted  with  other  crops  greater  care  must  be  given  to  irriga- 
tion than  otherwise,  since  these  other  plantings  will  draw  a  large  amount 
of  the  moisture  which  would  otherwise  be  available  for  the  walnut 
trees. 

FERTILIZATION. 

Very  little  of  a  specific  nature  can  be  said  upon  this  subject  since 
no  definite  data  are  available  in  connection  with  the  fertilization  of 
walnut  groves.  Fertilization  has  been  practiced  to  some  extent  by 
walnut  growers  and  an  extensive  experiment  was  arranged  and  carried 
on  for  several  years  at  one  time  by  ourselves.  In  no  case,  however, 
have  sufficiently  definite  results  been  obtained  to  justify  any  specific 
recommendations  in  regard  to  the  requirements  of  the  walnut  tree  in 
this  respect. 

The  experiment  mentioned  may  be  described  at  this  point. 

Fertilizer  Experiment. — A  cooperative  arrangement  was  made  with 
the  Cudahy  Ranch,  situated  just  south  of  the  city  of  Huntington  Park, 
near  Los  Angeles,  to  carry  on  a  fertilizer  experiment  upon  walnut  trees 
on  a  considerable  scale.  A  block  of  Santa  Barbara  Soft  Shell  seedling 
trees  was  chosen  for  this  purpose,  consisting  of  56  rows  of  21  trees 
each,  a  total  of  slightly  over  1,000  trees,  comprising  between  50  and  60 
acres  of  grove.  Each  of  the  various  fertilizers  or  combinations  used 
was  applied  to  two  rows  of  trees,  so  that  there  were  42  trees  in  each 
plot.  At  the  time  of  commencing  the  experiment  in  1907  part  of  the 
grove  was  five  and  part  six  years  old,  the  different  applications  being 
arranged  in  such  a  way  as  to  bring  about  comparative  tests  on  trees  of 
the  same  age.  The  soil  of  the  experimental  orchard  consisted  of  a 
sandy  loam,  being  decidedly  more  sandy  on  the  west  end  and  gradually 
becoming  heavier  toward  the  east.  The  rows  ran  north  and  south  so 
that  the  westernmost  plots  were  on  much  lighter,  sandier  soil  and  the 
trees  were  smaller  than  those  farther  east.  Except  for  these  smaller 
trees  at  one  end  the  grove  was  as  uniform  as  any  seedling  grove  of 
this  size  which  could  be  obtained.  This  variation  was  provided  for  by 
duplication  of  plots.     The  fertilizers  were  applied  for  two  successive 


186 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


years,  1907  and  1908,  all  expenses  being  met  by  the  Cudahy  Ranch. 
Applications  were  made  as  follows,  each  plot  consisting,  as  said  before, 
of  two  rows  or  42  trees : 


Plots. 

1907. 

Pounds  per 

tree. 

1908. 

Pounds  per 

tree. 

1  and  2 

No  fertilizer _ 

3 

Dried  blood 

10 
10 
15 
15 

Heavy 
0 

Heavy 

0 

40 

40 

30 

4 

Sulphate  of  potash 

10 

jSteamed  ground  bone      _. _ 

20 

5 

IBone  superphosphate 

20 

6 

Stable  manure __  __-  _ 

Heavy 

^Sulphate  of  potash _ 

5 

7 

(Stable  manure  _ 

Heavy 

8 

Dried  blood 

20 

9 

Bradley's  fruit  and  vine    : 

50 

10 

A.  0.  W.  walnut  fertilizer 

50 

11 

No    fertilizer   _  __      __       __ 

12 

Nitrate  of  soda 

24 
20 
30 
10 
10 

25 

13 

Sulphate  of  ammonia  _ 

20 

14 

Tankage 

35 

15 

Muriate  of  potash _ 

10 

16 

10 

17 

18 

No  fertilizer 

19 

35 

15 
15 
15 
20 

4 
15 

4 
15 
20 

4 
20 

40 

jSteamed  ground  bone .__  ___ 

20 

20  < 

/Superphosphate   

20 

25 

21 

•(Superphosphate 

40 

(Sulphate  of  potash 

10 

25 

22 

(Sulphate  of  potash 

10 

jNitrate  of  soda -    .    

25 

23 

j Superphosphate _ 

40 

\Sulphate  of  potash 

10 

24 

^Superphosphate   __  __    _ 

40 

25 

Sugar  factory  lime  (2  tons  per  acre  each  year)      . _ 

26 

No  fertilizer 

It  will  be  noted  that  many  of  these  applications  were  comparatively 
large,  costing  in  the  vicinity  of  $1.00  per  tree  per  year.  No  record  of 
the  crop  was  kept  until  1909,  when  a  careful  weighing  was  made  of 
the  crop  of  each  individual  tree  in  the  whole  experiment.  The  detailed 
results  will  not  be  given  in  this  bulletin  for  the  reason  that  they  were 
not  sufficiently  conclusive  to  warrant  their  publication.  So  far  as  the 
effects  of  the  various  fertilizers  were  concerned  no  conclusions  what- 
ever could  be  drawn.  This  is  due  partly  to  the  extreme  variation  in 
yield  of  the  individual  trees,  which  completely  obscures  any  effect 
of  fertilization,  and  also  to  the  fact  that  even  where  fairly  good  com- 
parisons could  be  made  the  fertilizer  applied  showed  a  surprising  lack 
of  decided  effect.  The  crop  on  the  various  trees  in  the  experiment 
varied  from  a  minimum  of  less  than  one  pound  up  to  a  maximum  of 
117.5  pounds.  With  such  a  range  it  is  almost  impossible  to  draw  any 
conclusions  from  the  effects  of  the  fertilizer,  even  when  the  crops  of 
the  42  trees  in  each  plot  were  averagd. 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  187 

The  most  valuable  results  obtained  from  the  experiment  were,  first, 
the  demonstration  of  the  variation  in  production  in  seedling  trees,  and 
second,  the  relation  of  soil  texture  to  walnut  production.  On  the  first 
point  we  may  repeat  what  has  been  said,  that  the  various  trees  varied 
from  one  to  117^  pounds  in  their  total  production. 

On  a  block  of  400  trees  on  fairly  uniform  soil  148  trees,  or  37  per 
cent,  produced  less  than  10  pounds  each;  118  trees,  or  29J  per  cent, 
produced  from  10  to  25  pounds  each;  82  trees,  or  20|  per  cent,  pro- 
duced from  25  to  50  pounds  each ;  26  trees,  or  9  per  cent,  produced  50 
to  60  pounds  each ;  10  trees,  or  2J  per  cent,  produced  60  to  75  pounds 
each;  5  trees,  or  1^  per  cent,  produced  75  to  100  pounds  each;  and  1 
tree,  or  J  per  cent,  produced  over  100  pounds. 

To  show  further  the  variation  in  production  in  seedling  trees  under 
almost  exactly  the  same  conditions,  the  crop  from  adjacent  trees  in 
some  of  the  individual  rows  may  be  stated.  In  row  20,  for  instance, 
the  production  in  pounds  per  trees  was  as  follows:  1.4,  16,  45.6,  10.5, 
21.5,  97.4,  20.5,  8,  26.3,  0,  16.4,  1,  18.6,  13.5,  10.6,  21.5,  2,  31,  .7,  14.8. 
Another  row,  3,  72.5,  32,  27.5,  58.9,  9.8,  69.5,  22.2,  30.5,  8,  44.5,  38.5, 
20.1,  19.1,  13.5,  34.8,  5.5.  In  the  case  of  the  117.5  pound  tree,  the  6 
trees  surrounding  it  produced  as  follows :  6,  24,  14,  28.5,  27,  23.  These 
were  all  Santa  Barbara  Soft  Shell  seedling  trees  in  their  eighth  year 
in  the  orchard  at  the  time  these  weighings  were  made.  The  same  vari- 
ation runs  through  all  the  figures  and  it  is  impossible  to  deduce  any 
reliable  conclusions  as  to  the  effect  of  the  fertilizers.  A  study  of  the 
figures  obtained,  taken  together  with  an  examination  of  the  trees  as 
to  general  appearance,  gives  one  a  fairly  strong  impression  that  the 
greatest  benefits  were  derived  from  the  application  of  stable  manure 
and  that  of  nitrogenous  materials.  Such  results  would  certainly  be 
expected,  especially  in  this  rather  sandy  land,  yet  even  so,  it  is  sur- 
prising to  note  the  lack  of  pronounced  results  from  the  application 
of  the  large  quantities  of  these  materials  which  were  used.  For 
instance,  in  the  plot  of  42  trees  which  received  during  the  two  years 
40  pounds  of  nitrate  of  soda,  60  pounds  of  superphosphate  and  14 
pounds  of  sulphate  of  potash  per  tree,  the  average  product  of  the  42 
trees  was  about  28  pounds  of  nuts.  In  the  plot  which  received  the 
same  minus  the  nitrate  of  soda,  the  average  product  was  exactly  the 
same ;  in  that  which  received  the  same  minus  the  potash  the  average 
was  33  pounds,  while  in  that  which  received  the  same  minus  the 
superphosphate  it  was  also  33  pounds.  These  plots  were  all  near 
together  on  the  same  type  of  soil  and  with  trees  as  uniform  in  appear- 
ance as  can  be  found  in  any  seedling  walnut  grove.  The  stable 
manure  plot  averaged  about  31  pounds,  while  the  adjacent  check  plot 


188  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

which  received  no  fertilizer  averaged  only  20  pounds,  which  difference 
is  the  only  striking  one  obtained  in  the  whole  experiment. 

The  effect  of  differences  in  soil  is  very  marked  in  comparing  the 
crops  of  the  west  and  east  ends  of  the  orchard,  on  the  light  and  heavier 
soils  respectively.  On  the  ten  west  rows  of  the  eight-year-old  trees, 
the  crop  averaged  16.3  pounds  per  tree,  while  on  the  ten  east  rows  of 
the  same  block  on  heavier  soil  it  averaged  30  pounds  per  tree.  These 
were  all  trees  of  approximately  uniform  appearance  and  not  especially 
stunted  where  the  smaller  yield  was  obtained.  The  westernmost  row 
averaged  7.56  pounds  per  tree,  while  the  easternmost  averaged  32.56. 
Between  the  two  the  average  production  per  row  graded  off  fairly  regu- 
larly regardless  of  the  fertilizer  used. 

The  results  of  this  experiment  are  typical  of  all  experience  in  ferti- 
lizing walnuts.  Many  attempts  have  been  made  to  determine  the  most 
effective  practice  in  this  respect,  but  all  of  these  have  shown  no 
positive  effect  on  account  of  variation  in  the  trees  and  an  apparent  lack 
of  response  to  fertilizers.  In  regard  to  walnut  fertilization  it  is, 
therefore,  impossible  to  offer  definite  advice  based  on  actual  experi- 
ments, but  the  most  that  can  be  done  is  to  suggest  such  practice  as 
may  reasonably  be  expected  to  give  good  results  with  any  crop  on 
California  soils.  We  know  in  general  that  nitrogen  and  phosphoric 
acid  are  our  most  needed  elements  and  that  the  application  of  these 
substances,  especially  on  older  plantings,  is  almost  certain  to  result  in 
improved  growth  and  vigor  in  almost  any  plant.  We  also  know  of  the 
walnut  that  individual  trees  produce  as  a  general  rule  in  proportion  to 
their  size,  and  that  the  larger  they  become  the  greater  crops  they  will 
bear.  It  is,  therefore,  our  conclusion  that  in  fertilizing  walnuts  nitro- 
gen and  phosphoric  acid  should  be  the  elements  most  largely  supplied. 

Along  with  fertilization  there  should  not  be  forgotten  the  importance 
of  keeping  the  soil  in  good  mechanical  condition,  especially  in  order 
that  it  may  absorb  and  retain  the  greatest  possible  amount  of  moisture. 
Indeed,  it  is  evident  from  the  results  of  the  Cudahy  experiment,  as 
well  as  from  general  observation,  that  this  factor  is  much  more  impor- 
tant, at  any  rate  for  several  years,  than  that  of  fertilization.  To  keep 
the  soil  in  good  condition  applications  of  stable  manure  are  very  effec- 
tive, likewise  the  growing  and  turning  in  of  green  manure  or  cover 
crops  to  as  great  an  extent  as  possible.  The  latter  practice,  in  southern 
California  at  least,  is  not  as  feasible  with  walnuts  as  with  the  citrus 
crop,  since  it  is  not  practicable  to  plant  the  crop  until  after  the  walnuts 
have  been  gathered,  which  brings  it  quite  late  in  the  season.  For  a 
cover  crop  in  walnut  groves  Canada  field  peas  have  been  found  one 
of  the  best  in  southern  California,  as  they  start  quite  readily  during 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  189 

the  winter.  In  addition  to  stable  and  green  manure,  if  other  fertilizer 
seems  desirable,  we  would  suggest  the  application  of  tankage,  or  dried 
blood  and  superphosphate,  either  of  which  supplies  nitrogen  and  phos- 
phoric acid  in  an  available  but  not  too  soluble  form. 

In  fertilizing  the  walnut  it  is  evident  that  comparatively  large 
quantities  of  material  must  be  used  to  obtain  any  real  effect.  The  idea 
of  applying  a  few  pounds  per  tree  of  any  substance  with  the  expecta- 
tion of  producing  some  specific  effect  upon  the  tree  or  nuts  is  absolutely 
futile.  With  large  trees  we  would  advise  not  less  than  50  to  100  pounds 
per  tree  of  high  grade  materials,  composed  largely  of  fairly  available 
nitrogen  and  phosphoric  acid,  if  any  real  effect  is  to  be  obtained. 
This  we  would  apply  during  the  winter  or  spring  at  the  time  of  plow- 
ing the  grove. 

PRUNING. 

The  pruning  of  the  walnut  tree  in  the  orchard  has  not  resolved 
itself  into  any  such  systematic  practice  as  is  the  case  with  most  fruit 
trees.  In  almost  all  of  our  present  groves,  in  fact,  no  pruning  at  all 
is  done,  save  that  most  growers  usually  go  through  each  winter  with 
an  ax  and  cut  off  all  the  limbs  which  have  come  down  upon  the  ground, 
in  order  to  facilitate  cultivation.  There  is  quite  a  common  impression 
that  walnut  trees  should  not  be  pruned  any  more  than  is  absolutely 
necessary  and  that  cutting  in  the  top  results  in  injury  of  some  sort  or 
other.  One  suggestive  fact  is  evident  with  the  walnut  tree,  however, 
namely  that  as  the  trees  grow  older  and  their  tops  closer  together  the 
setting  of  nuts  through  the  interior  of  the  tree  declines  very  notice- 
ably, and  also  that  trees  in  outside  rows  or  isolated  trees  which  stand 
out  by  themselves  produce  decidedly  more  heavily  than  those  in  the 
interior  of  the  orchard.  This  is  especially  noticeable  in  isolated  door- 
yard  trees,  which  are  almost  invariably  heavy  producers.  These  obser- 
vations have  led  some  growers  to  take  out  some  of  the  inside  limbs 
as  the  trees  become  older  and  more  crowded,  in  order  to  maintain  a 
better  exposure  to  the  air  and  sunlight.  Such  a  practice  is  in  our 
observation  an  excellent  one  and  we  would  recommend  in  the  case  of 
large,  old  trees  with  crowded  tops  that  a  considerable  amount  of  wood 
be  taken  out  in  the  center  of  each  tree  in  order  to  open  them  up.  In 
young  trees  little  pruning  is  ordinarily  necessary,  except  that  in  very 
windy  localities  it  may  be  necessary  to  keep  pruning  to  some  extent 
on  the  side  away  from  the  wind  in  order  to  counteract  the  tendency 
toward  a  one-sided  growth.  The  walnut  tree,  except  when  influenced 
by  wind,  has  a  very  strong  tendency  toward  symmetrical  development, 
regardless  of  the  form  in  which  it  starts.  If  a  large  limb  develops  on 
one  side  during  one  year's  growth  this  growth  usually  drops  back  the 
second  year  and  the  tree  develops  more  rapidly  on  the  other  side, 


190 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


bringing  it  back  into  a  symmetrical  form.  It  is,  therefore,  often 
better  to  let  the  tree  take  care  of  itself  in  this  way,  unless,  as  we  have 
said,  it  is  distorted  by  wind,  rather  than  to  try  to  balance  it  up  by 
pruning.  In  case  it  is  attempted  to  bring  young  walnut  trees  into 
symmetrical  form  by  pruning,  and  likewise  in  forming  the  tops  of  top- 
grafted  trees  which  have  a  tendency  to  become  very  top-heavy,  better 
results  seem  often  to  be  obtained  by  summer  pruning  while  the  trees 


B^W>jx'i  * 

m 

4." 

Mm 

^4uh 

P& 
&$§&& 

■ J'\ 

Br 

'.<•  '    "  "■■'.-.''"■    '.■'■."•'.  ••.-•;;.'-i..'--; '.  -"'.•■  •-..;  0..    . ..    • 

5  ,\  *  >  {• 

KM9S     Bvy  .W  itXf££s.: 

■""'  •       , 

Fig. 


22. — Santa  Barbara   Soft   Shell  seedling  walnut 

been   pruned. 


prove  in  which  the   trees  have  never 


are  in  full  growth  and  foliage  rather  than  by  cutting  off  limbs  during 
the  winter.  In  the  latter  case  large,  strong  suckers  are  apt  to  come 
out  at  every  cut  and  the  shape  of  the  tree  becomes  even  worse  than 
before.  On  the  other  hand,  by  cutting  back  the  green  shoots  while 
they  are  growing  their  growth  is  decidedly  checked,  while  those  of 
other  parts  of  the  tree,  being  in  an  active  condition,  develop  rapidly 
and  produce  the  effect  desired. 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  191 

Figures  22  and  71  illustrate  walnut  trees  which  never  have  been 
pruned  at  all,  the  branches  coming  down  upon  the  ground,  which  is 
the  natural  tendency  of  the  tree.  This  practice  is  not  without  its 
advantages,  although  it  is  doubtful  whether  the  latter  are  sufficiently 
great  to  warrant  its  general  adoption.  The  walnut,  like  the  lemon 
and  orange  and  some  other  trees,  seems  to  have  a  tendency  to  produce 
its  fruit  with  particular  abundance  on  branches  close  to  the  ground. 
It  is  certainly  true  that  such  branches  are  very  prolific  and  produce 
more  fruit  proportionately  than  those  higher  up  in  the  tree.  For  this 
reason  some  growers  consider  that  the  interference  with  cultivation  by 
these  low  branches  is  more  than  counterbalanced  by  the  increased  crop 
obtained.  This  is  largely  a  matter  of  personal  preference,  but  in 
most  orchards  a  higher-headed  tree  is  to  be  preferred.  In  the  young 
tree  shown  in  Fig.  71  the  object  of  the  owner  is  to  allow  the  trees  to 
take  this  form  during  their  early  life  in  order  to  obtain  quick  returns, 
while  as  they  grow  older  and  higher  it  is  his  intention  to  gradually 
prune  them  up.  Some  growers  may  find  it  profitable  to  follow  this 
method. 

Another  matter  which  may  be  discussed  under  the  subject  of  prun- 
ing is  that  of  the  breaking  off  of  large  limbs  of  walnut  trees,  which 
frequently  happens  especially  in  the  northern  part  of  the  State.  The 
large  lateral  branches  which  develop  from  the  main  stems  have  a  con- 
siderable tendency  to  form  a  very  poor  union  in  the  angle  of  the 
crotch  between  the  branch  and  the  stem  and  many  large  limbs  break 
off  at  this  point.  Trouble  of  this  sort  is  much  more  common  in  the 
northern  part  of  the  State,  possibly  on  account  of  the  fact  that  the 
growing  season  is  shorter  and  that  during  the  rapid  growth  of  the 
branches  the  crotch  joints  do  not  have  time  to  properly  unite.  Where 
such  large  limbs  break  off  nothing  can  be  done  but  to  make  as  clean 
a  cut  as  possible  at  the  point  of  breaking,  and  cover  the  wound  with 
paint  or  grafting  wax.  One  observation  upon  this  subject  is  of  value, 
namely,  that  in  the  walnut  there  are  usually  at  least  two  buds,  one  above 
the  other,  at  each  axil,  and  of  these  the  upper  bud  is  the  one  which 
normally  grows  out,  forming  these  branches  which  break  off  so  readily. 
It  has,  therefore,  been  suggested  that  in  localities  where  there  is  much 
trouble  of  this  sort  the  upper  bud  at  each  axil  where  a  limb  is  to  be 
produced  be  cut  off  and  the  second  bud  forced  into  growth,  with  the 
idea  that  this  lower  bud  will  form  a  branch  having  a  better  union. 
There  appears  to  be  considerable  value  in  this  idea. 


192 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


CROP  HANDLING. 

The  following  account  describes  the  methods  of  handling  the  walnut 
crop  most  generally  in  vogue  in  southern  California.  In  individual 
cases  various  deviations  from  the  methods  described  are  made. 


Fig.   23. — Top — Picking  walnuts.     Bottom — Washing;   cylinder  turned  by  horse  power. 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  193 

PICKING. 

Walnuts  are  gathered  by  picking  them  up  from  the  ground,  where 
most  of  them  fall  naturally  at  maturity.  When  the  nut  is  ripe  the 
outer  hull  opens  and  the  nut  falls  out  in  the  majority  of  instances. 
The  freedom  with  which  the  nut  leaves  the  husk  varies  somewhat  in 
different  seasons,  a  greater  proportion  of  nuts  falling  out  more  freely 
some  years  than  others.  Sticking  of  the  husk  to  the  nut  is  caused  by 
sunburn,  and  also  appears  to  be  due  largely  to  a  lack  of  soil  moisture, 
and  to  some  extent  to  a  dry  condition  of  the  atmosphere.  In  dry 
seasons,  as  a  rule,  the  husks  are  more  inclined  to  dry  down  tightly  over 
the  nuts  rather  than  opening  up  freely  while  still  green  and  succulent 
than  in  years  of  abundant  rainfall.  If  this  be  true,  the  benefit  of  irri- 
gation just  previous  to  the  ripening  of  the  nuts  is  very  apparent. 
The  nuts  are  usually  hurried  off  the  trees  to  some  extent  by  shaking,  the 
latter  operation  being  carried  on  by  means  of  long  poles  with  hooks  on 
the  end,  by  means  of  which  the  branches  can  be  shaken  without  injur- 
ing the  tree.  In  southern  California  walnut  picking  is  done  largely  by 
Mexican  families  who  camp  in  or  near  the  groves  during  the  season, 
while  young  and  old  of  both  sexes  take  part  in  the  work.  In  some 
cases,  however,  growers  are  now  employing  able-bodied,  adult  labor  for 
walnut  picking,  considering  such  labor  more  profitable  on  the  whole 
than  the  cheaper  class  more  commonly  employed.  Efforts  have  been 
made  to  perfect  machines  for  picking  walnuts  from  the  ground  by 
suction,  but  nothing  of  this  sort  has  as  yet  come  into  practical  use. 

WASHING. 

After  being  picked  up  and  placed  in  sacks  the  nuts  are  carried  to 
some  convenient  point  and  washed,  in  order  to  remove  dirt,  portions 
of  the  hull,  etc.,  which  may  be  sticking  to  them.  Such  washing  is  done 
in  large,  cylindrical  drums  made  of  coarse  wire  netting  in  which  the 
nuts  are  slowly  revolved  under  a  stream  of  water,  grinding  against 
each  other  and  against  the  wires  forming  the  sides  of  the  drum.  In 
this  way  all  the  nuts  which  have  fallen  normally  from  the  husk  and 
those  in  which  most  of  the  husk  has  been  removed  by  hand  during 
picking  are  very  thoroughly  cleaned.  For  removing  the  more  tightly 
attached  husks  of  the  sunburned  nuts  and  "stick-tights"  various 
devices  are  used,  consisting  in  a  general  way  of  cylinders  with  sharp 
projections  from  the  sides  by  means  of  which  a  considerable  propor- 
tion of  these  nuts  are  cleaned  up  fairly  well.  There  may  still  remain, 
especially  during  certain  seasons,  a  considerable  proportion  of  nuts 
with  fairly  good  meat  but  with  more  or  less  of  the  hull  tightly  adhering 
to  the  shell.  Such  nuts  are  sometimes  gone  over  again  by  hand,  remov- 
ing the  husks  which  can  be  gotten  off  without  too  much  effort,  but 
6—231 


194 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


ultimately  there  always  still  remains  a  greater  or  less  proportion  of 
these  "stick-tights"  which  must  be  picked  out  and  discarded. 

After  these  washing  and  other  cleaning  operations  are  over  the  nuts, 
now  in  a  dripping  wet  condition,  are  placed  in  large  trays  having 
bottoms  composed  of  slats  spaced  about  one  half  inch  apart,  so  that 


\J\ 


Fig.   24. — Top — Drying  nuts.     Bottom — Delivering  at  packing-house. 

the  nuts  may  drain.  These  trays  are  commonly  about  6  by  3  feet  and 
6  inches  deep,  thus  holding  several  layers  of  nuts.  The  side  boards 
are  allowed  to  project  at  the  ends  and  are  shaped  into  handles  for 
lifting  the  trays.  In  the  trays  the  nuts  are  stirred,  spread  out  in  the 
open  or  stacked  up  and  covered,  according  to  the  weather,  with  the 


Bulletin  231]  WALNUT   CULTURE   IN   CALIFORNIA.  195 

object  of  drying  them  as  rapidly  as  possible  without  too  great  exposure 
either  to  the  sun  or  to  moisture.  In  the  former  case  they  are  likely  to 
split  open,  especially  in  poorly  sealed  varieties.  In  the  latter  they 
may  become  moldy  and  discolored.  The  larger  and  more  progressive 
walnut  growers,  both  north  and  south,  are  coming  more  and  more  to 
the  use  of  artificial  heat  and  enclosed  buildings  for  drying  their  wal- 
nuts, rather  than  depending  upon  the  uncertainties  of  the  weather.  In 
this  way  the  nuts  can  be  dried  uniformly  and  quickly  with  no  danger 
of  exposure  either  to  rain  or  hot  sunshine.  In  the  northern  part  of 
the  State  where  early  rains  are  more  likely  to  occur  and  where  later 
varieties  of  walnuts  are  more  commonly  grown,  such  artificial  dryers 
are  an  absolute  necessity  in  handling  walnuts  on  a  large  scale  and  even 
in  southern  California  they  are  coming  into  use.  We  will  not  take 
space  to  describe  the  details  of  such  a  dryer  here  but  may  say  that 
a  very  large  and  complete  one  has  recently  been  installed  by  Mr.  J.  F. 
Burgess  of  the  Vrooman  Ranch,  Santa  Rosa,  which  is  well  worth  visit- 
ing to  one  contemplating  such  an  apparatus. 

After  drying  it  is  necessary  that  the  nuts  be  graded  to  some  extent 
at  home  in  order  to  remove  the  culls  and  worthless  nuts  before  delivery 
at  the  packing-house.  For  this  purpose  the  nuts  may  be  spread  out 
again  on  trays  or  handled  from  sack  to  sack  if  working  on  a  small 
scale,  while  on  a  larger  scale  an  arrangement  consisting  of  an  inclined 
bin  or  runway  large  enough  to  hold  several  sacks  or  even  several  tons  of 
nuts  is  desirable.  In  such  a  contrivance  the  nuts  pass  out  at  the  lower 
end  under  the  control  of  the  operator,  who  picks  out  the  culls  and  allows 
the  good  nuts  to  run  into  sacks,  in  which  they  are  carried  to  the 
packing-house.  Mr.  C.  B.  Franklin  of  Carpinteria  has  an  excellent 
arrangement  of  this  sort. 

PACKING-HOUSE  OPERATIONS. 

SAMPLING. 

According  to  the  methods  commonly  in  practice  in  southern  Cali- 
fornia the  walnuts  on  delivery  by  the  grower  at  the  packing-house 
are  first  sampled  for  quality.  The  inspector  picks  out  one  hundred  nuts 
here  and  there  at  random  from  the  sacks  and  cracks  each  one  to 
examine  the  meat  as  to  fullness  and  color.  There  are  various  require- 
ments as  to  quality,  but  usually  nuts  which  crack  from  80  to  90  per 
cent  of  sound,  fairly-light-colored  meats  will  pass.  The  standard  varies 
considerably  from  year  to  year,  according  to  the  general  quality  and 
quantity  of  the  crop  and  the  condition  of  the  market.  Not  over  10  per 
cent  of  badly  shriveled  or  entirely  bad  meats  is  often  accepted,  while 
in  color  it  is  usually  expected  that  45  or  50  per  cent  must  be  white  or 


196  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

very  light  brown,  and  from  30  to  35  per  cent  amber,  or  not  decidedly 
dark.  Having  been  accepted  by  the  inspector,  the  nuts  then  go  to  the 
bleach. 

BLEACHING. 

Various  methods  of  bleaching  walnuts  have  been  practiced,  the 
object  being  to  remove  all  dirt  and  discoloration  from  the  shells  and 
give  them  a  bright,  light  colored,  attractive  appearance.  In  the  earlier 
years  of  the  industry  most  of  the  nuts  were  bleached  by  exposure  to 
the  fumes  of  burning  sulphur,  this  being  done  while  they  were  wet. 
Sulphur  bleaching  is  quite  unsatisfactory,  however,  owing  to  the  fact 
that  the  fumes  penetrate  the  kernels  of  the  nuts  to  a  considerable 
extent  and  have  a  decided  effect  upon  their  flavor.  On  this  account 
sulphur  was  largly  abandoned  several  years  ago  and  a  process  of 
bleaching  the  nuts  by  immersion  in  a  liquid  took  its  place.  This  process 
consists  essentially  in  dipping  the  nuts  into  a  solution  of  chloride 
of  lime  and  sal  soda,  to  which  sulphuric  acid  is  added,  the  result  being 
a  liberation  of  chlorin  gas  which  brings  about  the  bleaching  action. 
The  following  formula  which  was  given  out  by  the  University  of  Cali- 
fornia Experiment  Station  illustrates  the  details  of  this  process :  ' '  Six 
pounds  bleaching  powder  (also  called  chloride  of  lime),  twelve  pounds 
sal  soda,  fifty  gallons  water.  Dissolve  the  bleaching  powder  in  abouj: 
four  gallons  of  water,  stirring  till  dissolved.  Dissolve  the  sal  soda 
in  about  four  gallons  of  water.  Add  one  solution  to  the  other  and 
stir  well ;  let  the  carbonate  of  lime  settle  to  the  bottom  and  draw  off  the 
clear  liquor  and  add  water  to  make  a  total  of  fifty  gallons.  Put  the 
nuts  in  large  dipping  box  or  lath  crate,  immerse  in  the  fluid,  and  then 
add  one  and  one  fourth  pounds  of  50  per  cent  sulphuric  acid  and 
agitate  by  raising  and  lowering  the  dipping  box.  The  bleach  should 
be  reached  in  five  to  ten  seconds,  and  the  nuts  are  then  washed  in  clear 
water  and  put  out  to  dry.  Of  course  to  employ  this  process  cheaply, 
specially  contrived  dipping  appliances  are  used.  The  same  liquor  can 
be  used  with  new  batches  of  nuts  so  long  as  the  proper  effect  is  pro- 
duced, and  small  additions  of  acid  will  prolong  the  efficiency  of  the 
liquor. ' ' 

Owing  to  litigation  over  the  rights  to  this  process  and  a  decision 
in  the  California  courts  that  it  was  covered  by  a  patent,  further  efforts 
were  made  by  the  walnut  growers  to  obtain  a  satisfactory  bleach  and 
quite  recently  they  employed  Professor  Stabler  of  the  University  of 
Southern  California,  Los  Angeles,  to  devise  a  new  process.  Professor 
Stabler  brought  into  use  the  electric  process,  consisting  essentially  in 
passing  an  electric  current  through  a  4  per  cent  solution  of  common 
salt  by  means  of  electrodes  immersed  in  the  liquid.  In  this  process 
chlorin  is  set  free  and  becomes  available  for  bleaching.     It  is  possible 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  197 

also  that  the  electric  current  may  exert  bleaching  action  of  its  own.  At 
all  events,  walnuts  bleached  in  this  manner  are  decidedly  free  from  the 
odor  and  taste  of  chlorin  which  characterized  many  of  those  bleached 
by  the  old  liquid  process.  In  the  electric  process,  as  first  applied,  the 
walnuts  were  immersed  directly  in  the  liquid  through  which  the  electric 
current  passed.  In  its  present,  more  improved  form  the  apparatus 
consists  of  a  comparatively  small,  porcelain  jar  or  cell  containing  the 
electrodes,  through  which  passes  a  continuous  stream  of  the  salt  water 
which  is  mixed  in  a  preliminary  tank,  passed  through  the  cell  for 
treatment,  and  goes  on  then  into  a  storage  tank.  The  bleaching  device 
proper  consists  of  a  series  of  slightly  sloping,  superimposed  narrow 
trays  with  coarse  wire  netting  bottoms,  down  which  the  nuts  are  made 
to  travel  slowly  by  means  of  a  shaking  device.  These  trays  are  placed 
one  beneath  the  other,  the  nuts  dropping  from  the  lower  end  of  the 
first  on  to  the  upper  end  of  the  second,  and  so  on,  back  and  forth  to 
the  bottom.  The  electrically  treated  salt  water  is  discharged  in  a  fine 
spray  over  the  top  tray  upon  the  nuts,  and  drops  down  through  upon 
them  more  or  less  as  they  travel  back  and  forth  in  traversing  the 
various  trays.  At  the  lower  end  of  the  apparatus  the  nuts  pass 
through  a  spray  of  clear  water  which  cleans  them  of  the  salty  solution. 
The  whole  apparatus  is  enclosed  in  a  tight  wooden  box  which  assists 
bleaching  to  some  extent  by  retaining  the  chlorin  gas.  This  electric 
method  of  bleaching  walnuts  is  still  in  process  of  development  and 
improvement,  but  the  results  thus  far  obtained  with  it  show  clearly  that 
it  is  far  the  most  satisfactory  method  yet  devised  for  bleaching  walnuts. 
The  nuts  after  treatment  have  a  very  beautiful,  attractive  appearance, 
without  the  dead,  unnatural  whiteness  which  is  given  to  them  by  strong 
sulphur  fumes  and  various  other  substances.  The  quality  of  the  nut 
is  seemingly  injured  not  at  all,  as  no  odor  remains  after  drying,  while 
in  respect  to  flavor  there  is  also  no  objectionable  effect.  The  only 
effect  of  this  sort  which  can  be  detected  is  in  the  case  of  nuts  which 
were  partially  open  when  passing  through  the  bleach,  which  may  have 
a  slight  salty  flavor.  On  leaving  the  bleaching  box  the  nuts  are  dis- 
charged on  to  a  moving  elevator  belt  which  carries  them  into  the 
grader. 

GRADING. 

In  this  operation  the  nuts  are  graded  into  two  sizes,  the  first  grade 
consisting  of  those  which  do  not  pass  through  an  inch  square  mesh 
screen,  while  No.  2s  are  those  which  will  pass  through  such  a  screen 
but  not  through  a  three  quarter  inch  square  mesh.  Various  devices 
for  grading  are  in  use,  some  consisting  of  a  cylindrical  cylinder  with 
sides  composed  of  a  wire  screen  of  the  proper  mesh,  while  more  com- 
monly they  are  graded  over  a  horizontal  screen  which  is  shaken  back 


198  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

and  forth  by  machinery  so  that  the  smaller  nuts  drop  through,  and  all 
sizes  are  carried  automatically  on  to  belts  which  elevate  them  into  bins 
for  drying  and  storage.  In  some  houses  artificial  drying  is  resorted  to 
at  this  point,  since  in  a  moist  climate  or  in  wet  weather  the  nuts  may 
become  moldy  and  discolored  before  drying.  More  or  less  grading  for. 
quality  is  done  after  the  nuts  leave  the  bleach  by  picking  out  discolored 
or  otherwise  objectionable  nuts  by  hand  at  some  convenient  point  in  the 
operation.  The  nuts  which  are  simply  discolored,  but  still  contain 
good  meats,  are  sometimes  run  through  the  bleach  a  second  time  and 
considerably  improved  in  appearance.  From  the  final  bins  the  nuts 
are  drawn  off  into  large  sacks  containing  about  100  pounds  each  for 
shipment  to  market. 

WALNUT  GRADES. 

The  commercial  grades  of  walnuts  commonly  made  in  California  are 
as  follows:  "Budded,"  No.  1  Soft  Shells,  No.  2  Soft  Shells,  No.  land 
No.  2  ' '  Standards  "  or  "  Hard  Shells, "  "  Paper  Shells ' '  and  culls.  The 
term  budded  walnuts,  as  commonly  applied  in  the  trade,  includes  the 
Placentia  Perfection,  or  nuts  of  equally  good  appearance  graded  over 
a  screen  one  and  three  sixteenths  inch  square  mesh.  Into  this  class 
go  all  the  good-sized  nuts  of  any  desirable  variety  which  is  worthy  of 
propagation  by  budding  or  grafting.  These  usually  command  a  pre- 
mium of  two  or  three  cents  per  pound  over  the  best  of  the  ordinary 
nuts.  The  terms  Soft  Shell,  Hard  Shell  and  Paper  Shell  are  of  rather 
uncertain  meaning  so  far  as  the  thickness  of  the  shell  is  concerned. 
As  a  matter  of  fact,  very  few  or  no  No.  1  Hard  Shells  go  on  to  the 
market,  but  almost  any  good-sized  nut  is  classed  as  a  Soft  Shell. 

"Hard  Shell"  and  "Paper  Shell,"  so  far  as  they  have  any  definite 
meaning,  refer  commonly  in  southern  California  to  certain  types  or 
varieties  of  trees  rather  than  to  nuts  of  a  particular  thickness  of  shell. 
' '  Hard  Shell ' '  means-  commonly  the  old-fashioned  walnut  of  the  first 
California  plantings,  which  is  a  tree  of  quite  characteristic  type.  The 
bark  is  of  decidedly  whitish  color,  the  general  form  of  the  tree  rather 
stocky  and  compact,  while  the  nut  is  small,  quite  round  and  decidedly 
hard-shelled.  The  tree  is  less  thrifty  and  more  inclined  to  die-back 
and  deterioration  than  the  prevailing  type  of  the  soft-shell  tree.  Com- 
paratively few  of  these  typical  hard-shell  trees  now  remain  in  the 
southern  California  groves.  Any  good  nut  of  desirable  size  and  shape 
goes  on  the  market  as  a  soft-shell,  regardless  of  its  actual  cracking 
quality,  so  that  extreme  thinness  of  shell  is  not  a  necessary  or  even  a 
desirable  quality.  Any  good-sized,  slightly  elongated  nut  is  decidedly 
better  from  a  commercial  standpoint  for  having  a  comparatively  hard, 
not  easily  opened  shell,  since  such  nuts  stand  handling  better  and  are 
also  less  liable  to  the  trouble  called  perforation,  which  we  describe  else- 
where. 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  199 

The  term  ''Paper  Shell"  also  denotes  a  certain,  quite  characteristic 
type  of  tree  rather  than  referring  to  any  or  all  nuts  with  unusually  thin 
shells.  The  Paper  Shell  of  southern  California  originated  almost  or 
quite  entirely  among  the  earlier  trees  propagated  by  Joseph  Sexton  of 
Goleta,  These  trees  are  of  quite  distinctive  character,  being  of  small 
size  as  compared  to  soft  shells  or  even  hard  shells  of  the  same  age,  with 
a  slender,  white  barked  trunk,  rather  large  leaves,  compact  top,  and  a 
small,  round,  more  or  less  thin-shelled  nut.  Some  typical  Paper  Shell 
trees,  however,  bear  nuts  which  are  not  especially  thin-shelled  and  all 
degrees  of  gradation  may  be  found  between  paper  shell,  soft  shell,  and 
hard  shell  trees.  The  typical  Paper  Shell  is  quite  similar  to  the  French 
variety  Chaberte  in  many  ways.  Most  paper  shell  trees  are  particularly 
susceptible  to  walnut  blight  and  the  variety  has  nothing  whatever  to 
recommend  it. 

selling. 

The  walnut  growers  of  southern  California  are  quite  generally  united 
into  cooperative  associations,  each  with  its  own  packing-house  and 
officers.  The  members  of  each  association  carry  their  nuts  to  their 
packing-house,  where  they  are  handled  and  sold  by  cooperative  methods. 
In  addition  to  these  various  local  associations  the  whole  industry  is 
organized  rather  loosely  into  one  general  organization  for  certain  lines 
of  business.  The  directors  of  the  local  associations  hold  a  combined  meet- 
ing at  least  once  a  year  and  keep  up  a  general  organization,  having  a 
president  and  the  other  usual  officers,  including  a  paid  secretary. 
Matters  of  general  interest  come  before  this  larger  meeting,  including 
the  purchase  of  sacks  for  each  season,  and  particularly  the  fixing  of 
prices  for  each  year's  crop.  At  a  meeting  held  each  year  early  in 
the  fall,  reports  and  estimates  are  submitted  as  to  the  probable  crop 
of  the  season  and  minimum  prices  are  fixed  for  nuts  of  the  various 
grades  for  that  year.  The  actual  selling  is  then  done  through  out- 
side brokers  who  receive  a  commission  for  their  services.  This  method 
of  selling  is  not  altogether  satisfactory  with  many  growers  at  present, 
and  the  suggestion  is  frequently  made  that  the  general  association 
employ  its  own  agents  in  the  various  trade  centers  all  over  the  country 
to  sell  the  crop  along  the  lines  practiced  by  the  California  Fruit 
Growers'  Exchange,  which  handles  the  bulk  of  the  citrus  crop.*  Grow- 
ers who  are  not  affiliated  with  any  association  usually  sell  their  nuts 
directly  to  brokers  or  commission  men  and  commonly  receive  associa- 
tion prices  for  the  same.  A  few  growers,  especially  in  the  northern 
part  of  the  State,  whose  orchards  are  composed  of  grafted  trees  of 
the  better  varieties,  have  a  special  trade  of  their  own  and  receive  from 
20  to  100  per  cent  more  for  their  nuts  than  the  ordinary  prices.     The 


*  Since  the  above  was  written  an  incorporated  central  association  has  been  formed 
along  these  lines. 


200  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

prices  received  by  the  southern  California  associations  during  the 
past  few  years  have  ranged  between  12  and  15  cents  per  pound  for  No.  1 
soft  shells,  about  1  cent  less  for  No.  1  hard  shells,  and  about  3  cents 
less  for  No.  2s  than  No.  Is.  Some  income  is  also  derived  from  culls, 
which,  if  fairly  good,  may  bring  at  least  5  cents  per  pound,  and  also 
from  the  selling  of  meats  which  are  removed  by  hand  from  the  broken 
or  very  poorly  sealed  nuts.  The  grower  usually  receives  about  one 
cent  less  per  pound  than  the  fixed  price,  this  difference  representing 
a  portion  of  the  broker's  commission  and  packing-house  expenses.  The 
remainder  of  these  expenses  is  covered  by  a  small  profit  made  by  the 
associations  on  the  sacks,  which  are  bought  through  the  general  asso- 
ciation at  very  low  rates. 

PROPAGATION  OF  THE  WALNUT. 

In  starting  a  walnut  orchard  various  methods  of  procedure  are  pos- 
sible. Till  of  which  have  their  merits  and  their  enthusiastic  supporters. 
Of  these  methods  the  three  following  are  most  important:  Planting  the 
njits  in  place  in  orchard  form  for  subsequent  grafting  when  the  trees 
are  large  enough ;  planting  nursery-grown  seedlings  in  orchard  form  for 
subsequent  grafting,  and  the  use  of  nursery-grafted  trees  for  orchard 
planting. 

ROOTSTOCKS. 

Inasmuch  as  various  roots  upon  which  to  grow  the  English  walnut 
are  available,  it  is  not  to  be  expected  that  any  one  species  will  necessa- 
rily be  the  best  under  all  conditions.  It  would  rather  seem  reasonable 
that  the  walnut,  like  most  fruit  trees,  would  do  better  on  some  soils 
or  under  some  conditions  upon  one  kind  of  root,  while  under  other 
conditions  a  different  root  would  be  most  suitable.  In  the  case  of  the 
walnut  much  still  remains  to  be  done  in  regard  to  testing  various  roots. 
The  planting  of  grafted  trees  is  so  recent  that  very  little  careful  test- 
ing has  been  done  and  in  the  majority  of  cases  it  is  only  known  in 
regard  to  the  root  that  they  are  "English"  or  "Black/'  the  latter 
including  all  sorts  of  forms.  After  discarding  the  English  root,  which 
nurserymen  have  now  done  quite  universally,  they  have  in  most  cases 
simply  gathered  nuts  from  the  most  convenient  black  walnut  trees,  and 
thus  we  have  among  the  so-called  black  walnut  roots  both  the  northern 
and  southern  California  species,  some  straight  eastern  and  many  hybrids 
of  various  mixtures  and  generations.  It  is  therefore  possible  to  tell 
very  little  from  existing  plantings  as  to  root,  since  it  would  be  necessary 
to  know  the  particular  tree  from  which  certain  seedlings  came  in  order 
to  duplicate  them.  A  few  of  the  most  advanced  nurserymen  have  com- 
menced in  recent  years  to  segregate  seedlings  of  the  various  species, 
hybrids,  arc1  ihose  from  certain  individual  trees,  and  it  is  only  in  this 


Bulletin  231]  WALNUT   CULTURE   IN   CALIFORNIA.  201 

way  that  roots  can  be  definitely  tested  on  different  soils  and  in  different 
localities  with  any  possibility  of  duplicating  the  same  roots  after  their 
qualities  have  been  determined. 

In  our  own  work  the  necessity  of  testing  rootstocks  as  well  as  differ- 
ent varieties  of  the  nut  itself  was  recognized  from  the  first,  and  in 
the  planting  of  our  experimental  orchard  on  the  Whittier  State  School 
grounds,  an  effort  was  made  to  obtain  trees  of  the  various  varieties  on  as 
many  different  roots  as  possible  when  the  first  planting  was  made. 
We  soon  found,  however,  that  the  roots  of  these  first  trees  purchased 
from  various  nurseries  came  a  long  way  from  representing  definite 
species  or  types,  but  that  as  a  matter  of  fact  they  were  a  very  much 
mixed  lot.  After  commencing  propagation  of  our  own,  root-testing 
was  still  kept  in  mind,  and  further  plantings  for  this  purpose  have  been 
made.  We  have  now  trees  growing  on  various  types  of  soil  in  various 
parts  of  the  State  and  on  different,  definitely  known  roots,  from  which 
plantings  results  of  some  value  can  be  looked  for.  A  few  other 
propagators  are  doing  the  same  thing.  Experience  has  abundantly 
proven  that  on  account  of  the  extreme  variation  in  the  seedlings  of 
various  black  walnut  trees  and  the  freedom  with  which  trees  hybridize 
or  cross  with  any  other  walnuts  in  the  vicinity,  the  matter  of  rootstock 
must  come  down  to  a  determination  of  the  qualities  of  the  seedlings  of 
certain  individual  trees  rather  than  those  of  all  the  trees  of  any  given 
species  or  form. 

The  general  requirements  in  a  root  are  that  it  should  produce  a 
thrifty  and  vigorous  tree,  the  more  so  the  better,  under  as  many  differ- 
ent conditions  as  possible.  In  other  words,  it  should  be  one  which  is 
not  easily  affected  by  unfavorable  conditions,  but  which  will  produce 
and  maintain  a  good,  thrifty  tree  even  if  the  ground  is  a  little  too 
dry  or  too  wet,  and  upon  as  many  different  types  of  soil  as  possible. 
Having  a  large  variety  of  types  to  choose  from,  however,  it  is  not  to  be 
expected  that  any  one  root  will  be  the  best  under  all  conditions  bat 
rather  that  we  shall  ultimately  find  one  type  to  be  the  best  for  dry  soil, 
another  the  best  where  there  is  an  excess  of  moisture,  one  for  heavy 
soils,  one  for  light  soil,  and  so  on.  At  the  same  time  a  good  all-round 
root  or  one  which  is  not  easily  affected  by  any  variation  from  its 
favorite  condition  is  by  far  the  best  for  general  purposes.  It  is  not 
impossible  that  we  shall  ultimately  find  a  difference  in  regard  to  varie- 
ties of  the  English  walnut  as  to  root,  some  kinds  doing  better  on  one 
root  and  others  on  another.  There  is  already  some  evidence  that  this 
is  true.  Prom  the  nurseryman's  *t-imlpoint,  it  is  desirable  that  a  tvpe 
be  chosen  for  the  root  wherein  the  parent  tree  is  a  large  producer  of 
nuts,  one  in  which  the  nuts  germinnte  readily  and  uniformly,  producing 
a  uniform  lot  of  seedlings  with  a  good  affinity  for  the  English  walnut. 


202  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

The  nurseryman  growing  any  considerable  number  of  trees  cannot 
afford  to  run  about  picking  up  a  few  nuts  from  a  tree  here  and  a  tree 
there,  even  though  they  may  give  seedlings  of  unusual  excellence.  Hav- 
ing found  good  trees  from  which  to  propagate,  some  nurserymen  are 
coming  to  the  practice  of  reproducing  a  considerable  number  of  these 
trees  by  grafting  and  planting  them  out  on  their  own  grounds  for  seed 
production  purposes. 

English  Walnut  Root. — The  propagation  of  the  English  walnut 
upon  its  own  root  has  been  almost  entirely  abandoned  in  California. 
This  is  on  account  of  the  fact  that  this  root,  while  very  vigorous  and 
thrifty  under  perfectly  favorable  conditions,  is  easily  affected  by  ad- 
versity and  very  susceptible  to  unfavorable  conditions,  either  perma- 
nent or  temporary,  such  as  dryness,  excessive  moisture  of  the  soil  or 
any  other  condition  not  perfectly  favorable.  The  English  root  delights 
in  a  deep,  fertile,  well  drained,  fairly  heavy  soil,  with  uniform  and 
abundant  moisture,  and  under  such  conditions  trees  grafted  upon  it 
are  thrifty  and  vigorous,  but  experience  has  shown  that  comparatively 
slight  variations,  such  as  dry  years  or  other  influences,  react  very 
quickly  and  unfavorably  upon  trees  on  this  root.  The  root  is  also 
more  susceptible  to  crown  gall,  gophers,  root  rot  and  some  other 
injurious  influences  than  are  those  of  any  of  the  black  walnuts.  For 
these  reasons  propagation  upon  the  English  root  is  practically  obsolete 
in  California. 

Eastern  Black  Boot,  Juglans  nigra. — This  root  has  been  tried  to 
some  extent  in  California,  but  the  species  is  of  such  extremely  slow 
growth  in  this  State  as  compared  with  other  black  walnuts  that  it  can 
scarcely  be  considered  as  a  commercial  root  for  general  use.  The  im- 
pression is  general  that  this  root  is  better  adapted  to  wet  land  than 
any  other,  on  account  of  the  native  habitat  of  the  tree  in  river  valleys. 
Even  under  such  conditions,  however,  it  is  probable  that  for  use  in 
California  a  better  root  can  be  chosen  for  planting  in  any  soil  which 
is  worthy  of  consideration  for  walnut  culture. 

Northern  California  Black  Root,  Juglans  hindsii. — The  black  walnut 
of  northern  California  is  an  extremely  thrifty,  vigorous  tree  under 
most  conditions  at  all  favorable  to  tree  growth,  and  this  is  one  of 
the  most  popular  and  satisfactory  roots  for  the  propagation  of  the 
English  walnut.  For  general  use,  where  no  special  study  of  selection 
of  rootstocks  is  made,  it  is  probably  the  best  root  which  can  be  recom- 
mended for  California  planting.  It  should  be  remembered,  however, 
that  the  progeny  of  various  individual  trees  of  this  species  vary  greatly, 
and  the  seedlings  of  some  trees  are  much  more  uniform  and  much 
better  trees  than  those  of  others.     Indiscriminate  planting  of  northern 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  203 

California  black  walnut  is,  therefore,  not  advisable  if  the  grower  desires 
to  produce  the  best  possible  trees  upon  this  root.  It  is  much  better 
to  plant  separately  the  nuts  from  various  trees  and  determine  the 
nature  of  the  offspring  in  each  instance.  Only  trees  of  large  produc- 
tion should  be  chosen  for  this  purpose,  since  it  is  not  profitable  to 
gather  nuts  here  and  there  from  a  great  many  different  trees.  Seed- 
lings from  the  best  types  of  the  northern  California  species  produce, 
when  worked  to  the  English  walnut,  a  thrifty,  vigorous  tree,  of  very 
good  growth,  more  resistant  both  to  excessive  moisture  and  drouth  than 
those  upon  the  English  root,  not  susceptible  to  gophers  or  root  rot,  and 
in  every  way  a  very  good,  all-round  tree.  The  root  is  only  excelled  by 
certain  special  hybrids  which  will  be  discussed  later. 

Southern  California  Black  Walnut  Root,  Juglans  calif ornica. — This 
root  has  been  quite  commonly  employed  for  the  English  walnut  in  the 
southern  part  of  California  and  has  much  to  recommend  it,  particularly 
for  that  part  of  the  State  where  it  has  been  most  tested.  The  quite 
common  impression  that  the  southern  California  walnut  root  has  a 
dwarfing  effect  on  trees  worked  upon  it  is  entirely  erroneous,  as  such 
is  certainly  not  the  case.  The  tree  no  doubt  gets  this  reputation  from 
the  fact  that  as  it  grows  wild  on  dry  hillsides  it  often  has  a  dwarfed, 
shrubby  form.  When  planted  in  good  soil,  however,  with  even  a  mod- 
erate supply  of  moisture,  it  is  a  tree  of  extremely  rapid  growth, 
especially  in  diameter,  and  actual  experience  shows  that  with  trees  upon 
this  root  there  is  no  indication  whatever  of  a  dwarfing  effect.  In  our 
southern  California  nurseries  we  have  found  no  walnut  which  gives  as 
uniform  a  growth  of  seedlings  in  the  row  or  as  uniformly  good  grafted 
trees  during  the  time  that  they  are  in  the  nursery  as  this.  From 
the  nurseryman's  standpoint,  in  the  south  at  least,  it  is  an  ideal 
tree,  the  nuts  sprouting  early  and  uniformly  and  the  seedlings  making 
a  uniform,  vigorous  growth  kept  up  until  very  late  in  the  fall.  Trees 
of  this  species  remain  green  and  still  growing  while  the  northern  Cal- 
ifornia and  other  forms  have  become  dormant  and  dropped  their 
leaves  in  the  fall,  while  in  the  spring  they  are  the  first  to  come  out. 
The  tree  is,  therefore,  especially  good  for  budding  on  this  account. 
The  southern  California  walnut  unites  readily  with  the  English,  and, 
as  we  have  said,  for  the  southern  part  of  the  State  at  least,  we  believe 
it  to  be  one  of  the  best  roots.  Other  objections  to  this  root  have  been 
that  it  is  especially  susceptible  to  wet  land  and  also  that  trees  grafted 
upon  it  are  more  apt  to  blow  over  than  those  upon  other  roots.  The 
first  objection  is  not  without  foundation,  since  the  southern  California 
walnut,  from  the  first  sprouting  of  the  nut,  is  extremely  susceptible 
to  an  excess  of  moisture.  This  root  should  not  be  used  for  trees  to  be 
planted  on  very  heavy  land  which  is  likely  to  be  extremely  wet  at  times. 


204  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

We  should,  in  fact,  hesitate  to  use  the  southern  root  at  all  for  the 
northern  part  of  the  State,  except  on  decidedly  light  soil.  One  should 
also  not  attempt  to  grow  it  in  a  nursery  where  the  soil  is  heavy  and  wet. 
In  this  connection  see  seedling  root  rot,  or  wilt,  page  379,  a  decay  of 
the  root  of  seedlings  in  very  wet  or  heavy  soil.  This  trouble  seems  to  be 
limited  to  this  species.  The  matter  of  the  trees  tipping  over  is  not 
usually  a  very  serious  objection,  although  such  trouble  does  seem  more 
common  on  this  root  than  on  any  other.  There  is  some  experience 
available  which  seems  to  indicate  that  for  late  varieties  like  Franquette 
and  Eureka,  the  southern  black  walnut  root  is  not  quite  as  well  adapted 
as  for  early  varieties  like  Placentia,  Chase,  or  Prolific.     With  the  latter 


Fig.  25. — Ten-year-old  Placentia  tree  on  southern  California  black  root. 

it  certainly  makes  a  magnificent  tree,  as  shown  in  many  existing 
orchards.  Even  with  the  late  varieties  it  makes  an  unusually  fine  tree, 
in  the  nursery  at  least,  and  the  most  uniformly  large  and  the  best 
stands  of  Eureka  which  we  have  ever  grown  were  on  this  root. 

HYBRID  ROOTS. 

The  remarkable  vigor  and  rapidity  of  growth  of  some  walnut  trees 
of  hybrid  origin  such  as  we  have  described  elsewhere  has  led  to  the 
very  natural  inference  that  seedlings  of  such  trees  should  be  extremely 
desirable  as  a  rootstock  for  the  English  walnut.  Working  on  this  idea, 
we  have  experimented  with  such  roots  quite  largely  during  the  past 
five  years  and  several  other  investigators  have  done  the  same. 


Bulletin  231] 


WALNUT    CULTURE   IN    CALIFORNIA. 


205 


Paradox  Hybrid  Boots.— It  would  seem  at  first  thought  that  seed- 
lings of  some  of  the  very  large,  wonderfully  thrifty  Paradox  hybrid 
walnut  trees  found  in   California  should  give  an  ideal  root  for  the 


Fig.  26. — Four-year-old  Placentia  tree  on  Paradox  root.     Trees  shown  in  Figs.  27  and 

28  in  the  background. 

English  walnut.     In  order  to  test  this,  nuts  from  many  of  these  trees 
have   been   planted  by  ourselves  and   others,   the  resulting  seedlings 


206 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 


grafted  to  various  varieties  of  the  English  walnut  and  the  trees  planted 
out  for  observation.  We  may  say,  however,  at  the  outset,  that  such 
trials  have  resulted  without  exception  in  proving  the  non-desirability 


Fig.  27. — Four-year-old  Placentia  tree  on  northern  California  black  root. 

of  the  seedlings  of  these  Paradox  trees  as  a  rootstock  for  the  English 
walnut.     Trees  on  this  root  are  invariably  lacking  in  any  unusual  vigor 


Bulletin  231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


207 


of  development  and  these  second-generation   Paradox  seedlings  may 
therefore  be  dropped  out  of  consideration. 

The  next  question  which  suggests  itself  is  the  possible  utilization 


Fig.  28. — Four-year-old  Placentia  tree  on  English  root. 

of  first-generation  Paradox  trees;  seedlings,  in  other  words,  which 
come  directly  from  black  walnuts  which  have  been  cross-fertilized  with 
pollen  of  the  English  walnut.     Such  trees,  as  we  have  shown  elsewhere, 


208  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

occur  in  a  greater  or  less  proportion  among  the  seedlings  derived  from 
black  walnut  trees  which  stand  in  the  vicinity  of  English  walnuts. 
These  seedlings  are  those  which  grow  into  the  extremely  vigorous  trees 
seen  here  and  there  in  the  State  and  it  is  certainly  to  be  expected  that 
an  English  walnut  upon  such  a  root  would  have  some  unusual  vigor. 
This  we  have  found  to  be  the  case,  by  grafting  upon  the  hybrids  which 
appear  here  and  there  among  the  black  walnuts  and  by  planting  out 
such  trees  for  future  observation.  We  cannot  yet  say  that  every  tree 
upon  a  first-generation  Paradox  root  will  have  this  unusual  vigor  but 
so  far  as  our  observation  has  gone  such  trees  have  a  general  tendency 
toward  such  a  habit.  Figs.  26,  27  and  28  illustrate  a  case  of  this  sort, 
these  being  Placentia  Perfection  trees  grafted  at  the  same  time,  of  uni- 
form size  when  planted  in  the  orchard  and  planted  adjacent  to  one 
another  under  uniform  conditions.  The  tree  on  the  Paradox  root  in 
Fig.  26  is  fully  twice  as  large  as  the  one  upon  the  English  root,  and 
decidedly  larger  than  the  one  upon  northern  California  black.  That  the 
production  is  proportionate  to  the  size  is  shown  by  the  crop  of  1911, 
when  the  Paradox  root  tree  produced  18J  pounds,  that  upon  California 
black  12J,  and  that  upon  English  9  pounds.  English  walnut  grafts 
unite  readily  with  the  Paradox  root,  which  is  a  very  desirable  feature 
from  the  nurseryman's  standpoint.  It  is  not  probable,  however,  that 
this  root  will  ever  be  largely  used  by  the  general  nurseryman,  since  only 
a  comparatively  small  and  very  uncertain  percentage  of  hybrid  trees 
develops  in  the  nursery,  extra  work  and  care  are  required  to  keep 
separate  the  trees  on  these  roots  from  those  on  the  straight  black  and 
only  one  who  is  something  of  a  specialist  and  who  is  able  to  make  a 
special  effort  to  obtain  and  segregate  these  roots  can  expect  to  make  a 
regular  practice  of  growing  trees  upon  them.  For  such  trees  he  must 
obtain  a  greater  price  than  that  received  for  those  on  ordinary  roots, 
in  view  of  the  extra  expense  and  care  necessary  to  produce  them. 
Good  Paradox  roots  are  especially  well  adapted  to  light,  dry,  or  rather 
sandy  soils,  as  this  hybrid  is  particularly  vigorous  under  such  condi- 
tions as  compared  to  any  of  the  ordinary  walnuts.  On  the  other  hand, 
trees  of  the  same  nature  have  sometimes  shown  themselves  likewise 
resistant  to  an  excess  of  moisture.  It  is,  therefore,  likely  that  the 
exceptional  vigor  of  this  root  enables  it  to  withstand  any  unfavorable 
condition  to  a  considerable  extent.  It  is  to  be  expected,  theoretically 
at  least,  that  Paradox  trees  containing  eastern  blood  would  be  better 
for  wet  land  than  those  consisting  of  English  and  California  black. 
Much  remains  to  be  done,  however,  in  testing  out  various  combinations 
and  especially  in  testing  the  seedlings  of  various  individual  trees 
under  various  conditions.  The  whole  question  of  the  value  of  hybrid 
roots  is  indeed  one  concerning  the  progeny  of  individual,  special  trees 


Bulletin  231]  WALNUT   CULTURE   IN   CALIFORNIA. 


209 


Fig.  29. — A  good  Royal  hybrid  root;  one  year  old.     Southern  Cali- 
fornia x  Eastern  black. 


7—231 


210  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

rather  than  a  matter  of  any  general  rules  applying  to  all  crosses  between 
certain  species. 

Royal  Hybrid  Boots. — Here  again  we  enter  the  domain  of  the  special- 
ist rather  than  that  of  the  average,  commercial  nurseryman.     We  have 
stated  elsewhere  that  in  the  Royal  hybrid  (the  cross  between  California 
and  eastern  black  walnuts)   many  very  thrifty,  vigorous  trees  occur 
and  that  this  vigor  is  carried  over  into  the  second  generation  much 
more  than  in  the  Paradox.     In  other  words,  experience  has  shown  that 
while  seedlings  from  Paradox  trees  do  not  have  the  exceptional  vigor 
of   the    parents,   there    are   some    first-generation   Royal   trees    which 
transmit  their  exceptional  rapidity  of  growth  to  their  progeny  of  the 
second  generation.     These  trees  vary  greatly,  however,  in  regard  to 
the  character  of  their  seedlings  and  it  is  only  a  very  few  which  produce 
nuts  that  give  a  uniform  lot  of  seedlings  as  good  as  the  parent.     Such 
trees,  when  found  and  thoroughly  tested,  are  extremely  valuable.     We 
wish  again  to  emphasize  the  fact,  however,  that  indiscriminate  plant- 
ing  of   nuts   from   Royal   hybrid   trees   cannot  be   expected   to   give 
uniformly  good  seedlings  for  grafting  purposes  but  rather  will  result 
in  a  most  heterogeneous  mixture  of  trees  of  all  sizes,  characteristics 
and  degrees  of  vigor.     The  Royal  trees  found  growing  about  the  State 
are  of  various  generations,  many  of  them  of  the  second  generation, 
of  which  the  seedlings   are  decidedly  inferior,   and  the  nurserymen 
would  do  better  to  plant  the  nuts  of  the  straight  northern  or  southern 
California  black  walnut  than  to  pick  up  Royal  nuts  at  random.     The 
propagation  of  English  walnuts  on  the  Royal  root  with  the  idea  of 
getting  trees  of  marked  superiority  over  those  grown  on  the  California 
species  is  again,  as  in  the  case  of  the  Paradox,  the  work  of  the  specialist 
who  is  disposed  to  try  out  individual  trees  carefully  as  to  the  nature 
of  the  seedlings  and  that  of  trees  grafted  upon  them,  a  process  which 
takes  several  years  in  the   case  of  each  individual  Royal  tree  thus 
tested.     Trees  of  real  excellence  upon  this  root  must  also,  therefore,  be 
grown  by  the   specialist   and   command   a   considerably   higher  price 
than  ordinary  trees.     It  should  be  equally  understood  that  really  select 
trees  on  these  exceptional  roots  constitute  the  very  acme  of  perfection 
in  walnut  trees  as  to  vigor  and  hardiness,  that  they  can  be  produced 
only  by  the  exceptional  nurserymen  and  probably  they  will  be  purchased 
only  by  growers  who  are  willing  to  pay  a  premium  in  order  to  obtain 
an   exceptional   orchard.     Trees  upon   well-grown   roots   of   either   of 
the  ordinary  California  species  are  thoroughly  good  and  first  class,  and 
need  not  be  deprecated  on  account  of  the  fact  that  it  is  possible  to  grow 
these  exceptional  trees  to  a  limited  extent  on  properly  selected  and 
tested  hybrid  roots.     Indiscriminate  trees  of  the  latter  class,  it  should 
also  be  understood,  are  no  better  than  and  perhaps  inferior  to  those  of 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  211 

the  former  nature.  The  best  Royal  hybrid  roots,  in  addition  to  giving 
trees  upon  them  of  exceptional  vigor,  are  also  particularly  adapted  for 
planting  on  rather  wet,  heavy  soils  on  account  of  the  blood  of  the  eastern 
black  walnut  which  they  contain.  Well  tested  Royal  roots  are  probably 
the  best  for  such  soil.  On  the  other  hand,  the  vigor  of  the  best  Royal 
root  enables  them  to  also  do  well  on  dryer  soils  or  without  irrigation, 
so  that  they  have  a  wide  range  of  adaptation. 

PLANTING  THE   NUTS   IN    PLACE. 

A  few  years  ago  a  very  popular  idea  prevailed,  especially  in  the 
northern  part  of  the  State,  that  the  only  proper  way  to  plant  a  walnut 
orchard  was  to  start  black  walnut  seedlings  directly  from  the  nut  in 
the  spots  which  the  trees  were  to  occupy  in  the  orchard,  so  that  these 
seedlings  could  be  grafted  to  the  desired  variety  of  the  English  walnut 
later  on  without  ever  disturbing  the  taproot  by  digging  and  trans- 
planting. In  order  to  insure  a  good  tree  in  each  place,  instructions 
were  given  to  plant  about  five  nuts  close  together,  like  a  hill  of  corn, 
at  each  point  where  a  permanent  orchard  tree  was  to  stand.  Out 
of  these  five  it  was  assumed  that  at  least  one  would  make  a  good  tree, 
and  that  this  could  be  allowed  to  remain,  while  any  others  were  to  be 
removed.  A  considerable  acreage  was  planted  and  is  still  being 
planted  in  the  northern  part  of  the  State  by  this  method.  Its  apparent 
cheapness  is  attractive,  and  the  idea  of  not  disturbing  the  root  has  also 
appealed  to  many  quite  strongly.  In  practice,  however,  we  may  say 
without  reservation  that  in  no  instance  do  we  know  of  this  method 
proving  practical  or  satisfactory.  The  objections  to  it  are  as  follows: 
In  the  first  place,  even  though  five  or  more  nuts  be  planted  in  each 
place,  there  are  always  in  a  large  planting  some  hills  where  for  one 
reason  or  another  no  trees  develop.  Some  will  produce  five  good  trees, 
others  none  at  all,  and  others  one  or  more  poor  trees  which  do  not 
become  fit  to  graft.  In  some  of  the  hills  very  thrifty,  rapid-growing 
trees  will  develop,  while  in  others  the  best  tree  will  be  of  poor  and 
slow  growth  and  thus  at  the  end  of  the  first  year  the  planting  will 
consist  of  trees  of  great  variation  in  size,  with  now  and  then  a  place 
where  there  is  no  tree  at  all.  This  variation  in  the  growth  of  the 
trees  becomes  greater  and  more  pronounced  as  years  go  on.  Further- 
more, in  planting  by  this  method,  which  presupposes  that  it  will  be  a 
number  of  years  before  any  walnuts  will  be  produced,  some  other  crop 
is  ordinarily  grown  on  the  land  in  the  mean  time,  and  in  cultivating 
this  crop  between  these  little  seedlings  it  is  impossible  to  avoid  a  tree 
here  and  there  being  run  over,  stepped  on,  or  destroyed  in  one  way 
or  another.  Again  a  rabbit  or  squirrel  may  get  one,  some  insect  pest 
another,  and  so  the  irregularity  of  the  planting  becomes  more  and  more 


212  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

pronounced.  Again,  it  is  impossible  to  give  to  trees  planted  out  in 
the  field  in  this  way  the  care  which  could  be  given  them  if  planted  in 
the  nursery,  and  their  growth  at  best  is  much  slower  than  it  would  be 
under  the  latter  conditions.  When  the  best  trees  finally  reach  graft- 
ing size,  there  are  bound  to  be  many  others  in  the  orchard  of  all  sizes 
and  ages  which  struggle  along  over  three  or  four  years  before  they  get 
large  enough  for  grafting.  After  grafting  commences  the  same  irreg- 
ularity continues.  In  some  trees  the  grafts  do  not  take  the  first  year, 
consequently  these  must  be  grafted  over  again  the  second  and  often  even 
the  third  year.  Thus  the  whole  tendency  of  this  method  in  practice  is  to 
produce  a  most  irregular,  uneven  orchard,  and  at  the  same  time  requir- 
ing several  more  years  for  its  development  than  is  necessary  under 
other  methods.  More  than  all  this,  the  absolute  fallacy  of  the  notion 
that  there  is  any  disadvantage  in  cutting  the  taproot  or  in  trans- 
planting the  walnut  tree  has  been  abundantly  established,  so  that  the 
only  object  of  using  this  method  loses  completely  its  value. 

PLANTING   BLACK  WALNUT  SEEDLINGS   IN   ORCHARD   FORM. 

This  method  represents  a  decided  improvement  over  the  last  one. 
It  consists  in  growing  black  walnuts  of  the  desired  type  in  the  nur- 
sery, then  selecting  from  these  as  good  and  uniform  a  lot  as  possible 
and  planting  them  out,  ordinarily  when  one  year  old,  in  permanent 
orchard  form,  with  the  idea  of  grafting  them  later  on.  By  doing  this 
several  of  the  objections  to  the  last  method  are  overcome.  It  is  pos- 
sible to  get  a  very  uniform  stand  of  black  walnuts,  provided  the  stock 
is  of  uniform  nature,  and  by  proper  selection  of  seedlings,  trees  can 
be  obtained  which  will  come  along  fairly  uniformly  and  be  ready  for 
grafting  at  about  the  same  time.  The  advantages  claimed  for  this 
method  are  mainly  two :  first,  that  by  allowing  the  black  walnut  trees 
to  reach  considerable  size  they  may  be  grafted  at  a  height  of  about  five 
feet,  thus  obtaining  a  black  walnut  rather  than  an  English  walnut 
trunk,  which,  with  its  rough  bark,  will  be  more  immune  to  sunburn. 
The  second  advantage  is  that  in  planting  an  orchard  to  be  grown 
without  irrigation,  grafts  upon  a  well  established  black  walnut  tree  will 
be  much  better  nourished  and  receive  a  better  supply  of  moisture  during 
the  first  year  or  two,  when  a  transplanted  tree  would  be  using  up  its 
energies  in  developing  new  roots,  and  thus  the  high-grafted  tree  will 
obtain  a  much  better  start.  Both  of  these  ideas  have  considerable 
merit,  especially  in  planting  where  irrigation  is  not  to  be  practiced. 
Under  such  conditions  a  vigorous  black  walnut  seedling,  especially 
if  dug  with  a  good  root  and  cut  back  in  the  top,  as  described  on  pages 
245  and  248,  may  usually  be  established  without  much  difficulty  by  a 
little  hand-watering  during  the  first  season.  If  the  soil  is  such  that 
non-irrigated  orcharding  is  at  all  feasible,  the  tree  will  then  go  on  to 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  213 

vigorous  development  in  subsequent  years.  A  nursery-grafted  tree,  if 
planted  at  the  same  time,  and  especially  under  rather  dry  conditions,  is 
likely  to  fall  behind  the  black  walnut  seedling  and  never  catch  up  to  it 
again  in  growth.  After  three  or  four  years  the  black  walnut  may  be 
cut  off  and  grafted  high,  whereupon  its  large,  vigorous  root  will  furnish 
the  grafts  with  an  abundant  supply  of  moisture  and  force  them  into 
rapid  development.  There  is  also  some  advantage  in  regard  to  sunburn 
in  the  black  walnut  trunk,  although  we  have  seen  such  injury  even  to 
the  black  walnut  on  rather  dry  soil.  It  is  also  true  that  sunburn  is  not 
apt  to  prove  serious  with  properly  grown  English  walnut  trunks  on 
good  soil. 

The  method  of  top-grafting  black  walnuts  in  place  is  open  to  one 
objection  in  common  with  that  of  planting  the  nuts  in  place,  namely, 
that  after  grafting  commences  a  uniform  stand  cannot  be  obtained  the 
first  year,  and  the  work  will  probably  extend  over  at  least  three  years 
before  all  the  trees  bear  a  good  top.  In  this  way  the  orchard  becomes 
irregular  and  uneven.  Again,  it  is  objected  with  considerable  reason, 
that  in  this  high  grafting  on  trees  several  years  old,  very  thrifty, 
rapid-growing  shoots  develop  from  the  grafts,  which  become  extremely 
top  heavy,  easily  blown  over  by  the  wind,  and  a  source  of  real  difficulty 
to  keep  up  in  shape  until  they  are  able  to  support  themselves.  On  this 
account  there  is  now  a  tendency  to  graft  low  on  such  trees,  within  two 
feet  of  the  ground,  even  though  most  of  the  supposed  advantage  of  the 
black  walnut  trunk  is  thereby  lost. 

Altogether,  we  may  say  that  if  the  walnut  orchard  is  to  be  planted 
in  good  soil  with  irrigation,  the  disadvantages  of  this  method  over 
planting  nursery-grafted  trees  by  far  outweigh  its  advantages.  At 
best  it  is  slow  in  producing  a  bearing  orchard,  it  results  in  much  irregu- 
larity in  the  size  and  growth  of  the  trees,  the  tops  are  very  difficult 
to  support,  and,  under  the  conditions  mentioned  of  good  soil  and  mois- 
ture, there  is  no  real  advantage  in  the  end  to  offset  these  objections. 
In  planting  a  walnut  grove  to  be  grown  without  irrigation,  especially 
on  rather  shallow  dry  soil,  where  the  trees  at  best  may  have  a  rather 
scanty  moisture  supply,  this  method  in  spite  of  its  disadvantages  is 
probably  the  best  one  to  use.  In  following  it  extra  good,  one-year-old 
seedlings  of  the  best  kinds  should  be  obtained,  these  to  be  treated  for 
planting  by  digging  with  as  much  root  as  possible  and  cutting  the 
tops  back  severely,  as  described  on  page  248,  planted  out  early  in  the 
winter  so  that  they  will  obtain  all  possible  benefit  of  the  winter  rains, 
and  given  all  possible  care  during  their  first  season's  growth.  A  good- 
sized  circle  should  be  kept  cultivated  or  hoed  about  each  tree,  they 
should  be  given  a  copious  watering  by  hand  as  many  times  as  possible 
during  the  first  season,  and  it  is  well  to  dig  into  the  soil  about  them  a 


214  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

good  dressing  of  stable  manure  with  a  heavy  mulch  of  the  same  mate- 
rial, in  order  to  retain  moisture  as  well  as  add  fertility  to  the  soil. 

As  the  trees  grow  they  should  be  staked  up  if  necessary  and  trained 
to  a  single  stem  which  eventually  should  be  cleared  of  side  branches 
up  to  about  five  feet.  It  is  not,  however,  necessary  or  desirable  to  prune 
the  tree  to  a  single,  bare  shoot  from  the  very  first,  since  side  branches 
shade  the  trunk  from  the  sun  and  also  assist  in  growth,  particularly  that 
in  diameter.  It  is,  therefore,  better  to  take  off  the  laterals  gradually 
from  below  at  the  end  of  each  season  rather  than  keeping  them  all 
cleaned  off  continuously.  For  the  best  success  of  this  method  it  is  not 
well  to  hasten  the  grafting  too  much,  as  better  permanent  results  will  be 
obtained  by  allowing  the  trees  to  reach  considerable  size  before  graft- 
ing. Grafting  when  the  trees  are  less  than  three  inches  in  diameter 
at  a  point  five  feet  from  the  ground  is  of  doubtful  advisability,  and  it 
is  better  to  wait  until  most  of  the  trees  in  the  orchard  have  reached 
at  least  this  size  before  commencing  grafting.  It  is  not  advisable  to 
graft  each  year  a  few  of  the  largest  trees,  thus  scattering  the  grafting 
over  several  years,  on  account  of  the  unevenness  of  an  orchard  treated 
in  this  way.     For  methods  of  top  grafting,  see  page  230. 

RAISING  THE  TREES   IN   THE   NURSERY. 

This,  as  we  have  shown  in  discussing  other  methods,  is  ordinarily 
much  the  most  satisfactory  and  successful,  and  the  quickest  and  cheapest 
method  of  starting  a  walnut  grove. 

SEED  TREATMENT. 

Walnuts  to  be  used  for  planting  in  the  nursery  should,  after  gath- 
ering, be  kept  in  sacks  or  other  receptacles  in  a  cool,  not  too  dry  place 
until  planting  time.  If  allowed  to  become  extremely  dry  after  gath- 
ering the  nuts  germinate  much  less  easily  than  otherwise.  They  will 
usually  keep  in  good  condition  if  tied  up  in  sacks  and  piled  in  a  cool, 
shady  place.  It  may  be  found  desirable  to  allow  the  outer  hulls  to 
dry  somewhat  before  sacking  up  the  nuts,  especially  in  the  case  of  large 
hybrid  nuts,  since  if  sacked  and  put  away  quite  green  the  hulls  decay 
and  become  extremely  soft  and  mushy.  Early  in  the  winter,  not  much 
later  than  January,  the  nuts  should  be  layered  in  sand  or  light  strawy 
earth  in  order  to  sprout  them  and  segregate  the  best  ones  from  those 
that  germinate  feebly  or  not  at  all.  This  is  most  conveniently  done  by 
constructing  a  frame  about  18  inches  deep,  either  above  or  below 
ground,  in  the  bottom  of  which  should  be  placed  3  or  4  inches  of  sand, 
then  the  layer  of  nuts  which  may  be  either  one  or  several  nuts  in  depth, 
according  to  the  available  space.  The  nuts  are  then  covered  with  3 
or  4  inches  of  sand,  which  should  be  washed  down  thoroughly  between 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  215 

the  nuts  by  means  of  a  stream  of  water.  The  whole  bed  will  thus  be 
in  a  well-soaked  condition  by  the  time  it  is  done.  Instead  of  placing 
the  nuts  directly  in  the  bed,  it  is  more  convenient  in  getting  them  out 
to  put  them  in  shallow  wooden  boxes  or  flats,  imbedding  these  in  the 
sand  as  above  described.  If  this  is  done  it  is  much  easier  to  get  the 
nuts  out  for  planting  than  if  they  are  placed  directly  in  the  sand. 
Other  materials  may  be  substituted  for  sand,  such  as  earth  mixed  with 
fine  straw  or  manure,  or  any  substance  which  holds  moisture  well,  and 
from  which  the  nuts  can  be  easily  removed.  The  bed  should  be  so 
arranged  that  water  will  drain  away  from  it  and  not  accumulate 
sufficiently  to  rot  the  nuts,  and  it  should  be  protected  from  rain  if 
there  is  any  danger  of  such  an  effect  from  that  source.  The  nuts  need 
to  be  constantly  well  moistened,  however,  in  order  to  start  germina- 
tion, and  if  drainage  is  good  there  is  not  much  danger  of  getting  them 
too  wet.  The  bed  should  be  located  in  a  place  where  it  will  receive 
the  heat  of  the  sun  in  order  that  it  may  not  be  too  cold  for  germination, 
and  it  may  be  underlaid  with  manure  if  it  is  desirable  for  any  reason 
to  hasten  the  sprouting  of  the  nuts.  Nuts  of  the  different  species 
vary  quite  widely  in  respect  to  freedom  of  germination,  those  of  the 
southern  California  black  walnut  being  especially  quick  to  sprout. 
These  also  rot  more  easily  than  other  black  walnuts.  They  need  not, 
therefore,  be  put  into  sand  so  early  and  should  not  be  kept  as  wet  as 
northern  California  blacks  or  Royals.  The  latter  especially  need  much 
moisture  and  warmth  to  make  them  sprout.  For  prompt  and  uniform 
germination  they  should  be  put  into  the  sand  quite  early,  in  a  single 
layer  of  nuts,  and  be  kept  well  moistened  and  as  warm  as  possible. 
Otherwise  many  will  not  sprout  until  the  second  or  even  third  year,  if 
they  be  put  into  the  ground  before  starting  to  germinate. 

As  soon  as  a  considerable  portion  of  the  nuts  has  begun  to  sprout 
in  the  sand  bed  they  must  be  gotten  out  into  the  nursery  as  soon  as 
possible.  In  preparing  the  nursery  ground  special  care  should  be 
taken,  as  the  growth  of  walnut  seedlings  is  very  easily  affected  by 
slight  differences  in  soil  conditions.  The  ground  should  be  prepared 
in  the  fall  by  thorough  and  deep  plowing  and  cultivation,  in  order  that 
it  may  be  loosened  up  to  as  great  a  depth  as  possible  and  brought  into 
a  fine,  mellow  condition,  free  from  lumps  and  with  no  hard  layer  of 
soil  near  the  surface.  A  soil  free  from  rocks,  hard,  unbreakable  lumps 
or  shallow  hardpan  should  be  chosen  for  the  nursery  if  one  expects  to 
grow  good  trees.  Greater  growth  is  obtained  on  a  fairly  heavy  soil, 
although  the  heavier  the  soil  the  more  difficult  it  is  to  work.  The 
future  digging  of  the  trees  should  also  be  considered,  as  this  is  a 
question  of  importance  in  connection  with  the  nature  of  the  soil.  A 
somewhat  sandy  soil  is  easier  to  handle  and  much  more  convenient  for 


216  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

getting  out  the  trees  when  ready  for  market  than  a  heavy  soil,  as  the 
latter  is  likely  to  be  muddy  and  unworkable  at  the  time  when  the 
trees  should  come  out.  Larger  trees,  however,  are  grown  on  heavy  soil 
and  big  trees  commonly  bring  the  best  prices.  By  means  of  fertiliza- 
tion and  an  abundant  use  of  water,  the  growth  of  trees  on  lighter  soil 
may  be  accelerated  to  a  considerable  extent.  Walnut  nursery  trees 
are  grown  more  or  less  without  any  irrigation  at  all  in  the  northern 
part  of  the  State,  but  under  such  conditions  only  a  fairly  heavy  soil 
with  strong  water-retaining  properties  should  be  considered. 

In  planting  the  nursery,  rows  about  three  feet  nine  inches  apart 
should  be  furrowed  out  with  a  single  plow,  and  the  best  sprouted  nuts 
may  then  be  planted  at  a  distance  of  from  nine  to  twelve  inches  apart 
in  the  row.  Particular  care  is  desirable  at  this  point,  placing  the 
nuts  carefully  in  place  by  hand  with  the  sprout  pointing  straight  down 
rather  than  dropping  them  in  indiscriminately  regardless  of  position. 
In  practice  it  will  be  found  that  some  of  the  sprouts  have  made  several 
inches  growth  before  planting  commences  and  these  should  be  handled 
carefully  and  planted  with  a  trowel.  It  is  well  for  the  planter  to 
carry  such  a  tool  in  one  hand,  filling  up  the  low  places  in  the  furrow, 
digging  holes  for  the  longer  sprouts  and  planting  each  nut  as  carefully 
as  possible.  In  some  cases,  on  account  of  rainy  weather  or  other 
reasons,  it  is  impossible  to  start  planting  early  enough  and  many  of  the 
nuts  will  form  long  sprouts  and  commence  sending  up  a  stem  before 
planting.  These  can  still  be  planted  out,  although  the  work  requires 
more  care.  Boot  sprouts  which  are  several  inches  or  a  foot  or  more  in 
length  usually  become  broken,  but  will  still  grow  successfully  if  not 
broken  off  close  to  the  point  where  they  come  from  the  nut.  It  is 
indeed  advisable  to  cut  back  long  sprouts  to  a  length  of  a  few  inches 
rather  than  attempting  to  preserve  each  one  and  dig  a  deep  hole  for  it. 
Such  trees  will  often  form  a  large,  branching  root,  more  desirable  than 
one  produced  by  the  uninterrupted  growth  of  the  original  tap  root. 
If  the  upward-growing  sprout  be  broken  off  the  nut  should  be  dis- 
carded. It  may  sometimes  be  necessary  to  go  over  the  bed  two  or  more 
times  in  order  to  get  all  the  good  nuts  out  before  the  earliest  have  made 
too  much  growth.  For  growing  the  best  trees,  however,  only  the  nuts 
which  germinate  most  promptly  and  vigorously  should  be  used,  and  it 
will  be  found  necessary  to  discard  a  considerable  percentage  of  the  nuts 
placed  in  the  sand.  After  planting,  the  nuts  should  be  covered  to  an 
average  depth  of  about  three  inches,  which  may  be  done  with  a  single 
plow,  if  the  nursery  is  large,  going  over  the  ground  afterwards  with  a 
harrow  in  order  to  smooth  over  the  irregularities  and  even-down  the 
ridges.     Special  care  should  be  taken  not  to  plant  too  deep. 

If  the  nuts  have  been  well  sprouted,  the  seedling  trees  will  soon  begin 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  217 

to  appear  above  ground,  although  if  heavy  rains  occur  before  this  time 
the  surface  may  crust  over,  especially  on  heavy  soils,  to  such  an  extent 
as  to  make  it  difficult  for  the  young  sprouts  to  break  through  the  surface. 
Under  such  conditions  it  may  be  well  to  go  over  the  nursery  with  a  rake 
or  light  harrow  in  order  to  break  up  this  crust.  As  the  trees  grow  they 
should  be  given  good  care,  such  as  would  be  given  to  a  crop  of  corn  or 
potatoes,  by  frequent  cultivation  and  hoeing.  Seedlings  are  grown 
without  irrigation  in  some  localities,  and  there  is  a  fairly  common 
impression  that  such  trees  are  more  hardy  and  desirable  than  those 
grown  under  irrigation.  We  cannot  coincide  with  this  view,  however, 
having  found  no  undesirable  features  in  irrigated  trees,  while  their 
superior  growth  is  desirable  from  every  standpoint.  As  ordinarily 
grown  without  irrigation,  two  seasons'  growth  is  necessary  to  get  the 
majority  of  the  seedlings  up  to  sufficient  size  for  grafting,  while  with 
good  soil  and  abundance  of  water,  fine  large  trees  of  ample  size  for 
grafting  can  be  produced  in  one  year,  with  roots  proportionate  to  the 
top  in  size  and  with  no  undesirable  qualities  whatever  on  account 
of  having  been  given  sufficient  moisture  for  their  best  development. 
The  difference,  in  fact,  is  fully  as  apt  to  be  in  the  other  direction,  non- 
irrigated  trees  being  stunted  and  reaching  grafting  size  only  after 
several  years'  growth.  Again,  in  unusually  dry  years,  non-irrigated 
trees  may  be  badly  injured  or  even  killed  by  drouth. 

GRAFTING. 

With  good  care  and  sufficient  moisture  the  majority  of  the  seedlings 
should  reach  sufficient  size  for  grafting  during  their  first  year's 
growth  and  be  ready  for  grafting  during  the  next  winter  following 
that  when  the  nuts  were  planted.  The  size  of  tree  which  is  suitable 
for  grafting  depends  largely  upon  the  size  of  the  scions  available, 
since  seedlings  can  be  used  nearly  down  to  the  size  of  the  smallest  good 
scions.  In  practice  it  will  be  found  that  trees  of  from  one  to  two  inches 
in  diameter  close  to  the  surface  of  the  ground  are  best  adapted  for 
grafting,  while  with  the  best  of  the  smaller  scions  trees  down  to  that  of 
three  quarters  of  an  inch  or  a  little  less  may  be  used.  This  assumes 
that  the  trees  are  grafted  close  to  the  ground. 

There  are  various  methods  of  nursery  walnut  grafting  in  practice, 
the  majority  of  which  we  will  not  attempt  to  describe.  The  operation 
at  best  is  one  which  requires  much  skill  and  practice,  the  walnut  being 
less  easily  grafted  than  most  fruit  trees,  and  among  those  who  are 
doing  the  work  successfully  each  has  his  own  method  to  which  he  has 
accustomed  himself  by  long  use  and  which  might  hold  no  particular 
advantage  for  the  beginner.  We  will,  therefore,  describe  but  one 
method  of  nursery  grafting,  which  is  that  which  has  proven  most 
successful  with  us. 


218 


UNIVERSITY    OF    CALIFORNIA  —  EXPERIMENT    STATION, 


Time  of  Grafting. — The  time  most  commonly  chosen  for  grafting 
walnuts  in  the  nursery  is  the  period  just  before  the  seedling  trees 
commence  growth  in  the  spring,  or  even  after  the  buds  have  unfolded 
and  the  leaves  developed  to  some  extent.  Various  ideas  will  be  found 
upon  this  subject,  and  it  may  also  be  said  that  results  vary  to  a  con- 


Fig.  30. — Face  and  side  view  of  scion  for  nursery  graft. 
These  are  somewhat  larger  than  the  most  desir- 
able size. 


siderable  extent  from  year  to  year,  even  though  the  grafting  is  done  at 
apparently  the  same  stage  of  development.  The  best  average  results, 
however,  have  been  obtained  by  commencing  the  work  just  in  time  to 
complete  it  as  the  seedlings  are  coming  into  leaf. 

In  grafting  by  the  method  which  we  shall  describe,  the  first  operation 


Bulletin  2  31]  WALNUT    CULTURE   IN    CALIFORNIA.  219 

consists  in  hoeing  away  the  dirt  from  about  the  seedlings  in  such  a 
manner  as  to  expose  the  trunk  down  to  the  crown  of  the  root.  Several 
inches  of  surface  soil  must  be  soft,  moist  and  mellow  at  this  time,  and 
if  not  already  in  this  condition,  they  must  be  made  so  by  irrigation, 
cultivation,  or  whatever  method  is  necessary.  The  young  trees  are  then 
cut  off  with  pruning  shears  or  a  saw  close  above  ground.  With  a  sharp 
grafting  knife  the  operator  then  cuts  a  sloping  bevel  on  one  side  of  the 
stub  and  then  with  his  knife  splits  the  stub  down  on  this  side  for  about 
an  inch,  as  shown  in  Fig.  31 — 1. 

The  Scion. — Scions  of  the  desired  variety  should  be  chosen  and  cut 
from  the  tree  at  some  time  during  the  winter  after  growth  has  ceased 
and  the  tree  become  dormant,  choosing  scions  from  the  most  productive 
and  best  trees  and  branches.  Most  propagators  prefer  to  cut  their 
scions  some  little  time  ahead  of  the  time  of  grafting,  as  they  consider 
a  sort  of  curing  process  beneficial.  The  best  wood  for  scions  consists 
commonly  of  that  of  the  previous  season's  growth,  bearing  well-formed 
buds  fairly  close  together,  and  with  as  much  as  possible  of  solid  wood 
rather  than  pith.  Occasionally  two-year-old  wood  may  be  used  for 
scions,  but  such  wood  commonly  is  deficient  in  good  buds.  Some  con- 
sider only  terminal  buds  desirable  for  scions  and  use  therefore  simply 
the  tips  of  the  shoots,  but  lateral  buds  develop  equally  well  and  their 
use  enables  the  propagator  to  utilize  his  wood  to  a  much  greater  extent. 
Grafting  wood  is  commonly  cut  up  into  sticks  about  one  foot  in  length, 
each  of  which  bears  from  4  to  6  buds  if  the  wood  is  of  the  most  desir- 
able form.  During  the  period  between  cutting  the  scions  and  the  time 
of  grafting,  the  wood  must  be  stored  in  such  a  manner  that  it  will  retain 
its  moisture  and  vitality  without  at  the  same  time  getting  too  wet  and 
becoming  water-logged.  There  is  commonly  more  danger  of  the  scions 
becoming  too  wet  than  too  dry,  unless  they  are  carefully  handled.  With 
some  it  is  the  practice  to  bury  the  grafting  wood  in  moist  sand,  which 
method  is  good  provided  the  sand  is  not  kept  too  wet.  In  this  method 
the  grafting  sticks  should  be  buried  in  sand  which  is  barely  moist,  and 
watched  carefully  to  see  that  they  are  kept  from  extreme  dryness, 
without  at  the  same  time  keeping  the  sand  decidedly  wet.  There  is 
some  objection  to  this  method  on  the  ground  that  more  or  less  sand 
clings  to  the  scions  and  tends  to  dull  the  knife  and  adhere  to  the 
surface  of  the  cuts  in  grafting.  Others  keep  their  scions  in  moist 
sawdust  or  sphagnum  moss,  which  does  away  with  the  latter  objection 
and  keeps  the  scions  in  good  condition,  provided  again  it  is  not  made 
too  wet.  We  have  found  sawdust  the  most  satisfactory  material. 
Others  place  the  scions  in  a  cool,  out-of-door  shed  with  only  the  butt 
ends  stuck  into  moist  sand  or  sawdust,  leaving  a  considerable  part  of  the 
length   exposed  to  the   air.     Whatever  method  is   followed  the   chief 


220 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 


consideration  is  to  keep  the  wood  barely  moist  without  soaking  and 
water-logging  it.  In  the  latter  case  the  wood  becomes  dark  colored 
and  if  in  this  condition  should  be  cut  off  and  discarded  in  grafting. 
Scions  properly  kept  will  remain  in  good  condition  for  several  months, 
often  callousing  over  on  the  ends  if  kept  until  late  in  the  spring. 


Fig.   31. — 1,   Splitting  the  stock  for  nursery  graft;    2,   Scion  inserted  and  tied; 
3,   Waxing ;   heating  stove  at  the  right. 

Grafting. — In  grafting,  the  sticks  should  be  cut  up  into  lengths 
bearing  at  least  two  buds  each,  one  near  each  end.  The  operator 
provides  himself  with  a  considerable  supply  of  such  scions  which  he 
carries  along  in  a  pocket  apron,  box,  or  basket.  In  grafting  he  makes 
a  long,  clean,  sloping  cut  on  one  end  of  the  scion,  on  the  side  opposite 


Bulletin   231]  WALNUT    CULTURE    IN    CALIFORNIA.  221 

the  bud.  The  surface  of  this  cut  should  be  smooth  and  uniform  and 
it  is  usually  made  by  the  experienced  operator  in  one  stroke.  A  split 
is  then  made  with  the  knife  between  the  bark  and  the  pith  on  the  longer 
side  of  the  scion,  this  split  extending  nearly  down  to  the  bud.  It  is 
made  nearer  the  bark  than  the  pith,  raising  only  a  thin  chip  of  Avood 
with  the  bark.  For  each  stock  a  scion  is  chosen  a  little  smaller  in 
diameter  than  the  stock,  the  larger  scions  being  put  upon  the  largest 
stocks,  and  vice  versa.  Fairly  large  stocks  are  always  desirable,  espe- 
cially in  propagating  new  varieties  where  grafting  wood  is  scarce,  as 
upon  them  can  be  used  both  large  and  small  scions.  The  stock  should 
not,  however,  greatly  exceed  the  scion  in  size,  since  in  such  a  case 
complete  healing  over  may  not  take  place  the  first  year.  After  split- 
ting the  scion  it  is  inserted  upon  the  split  in  the  stock  as  shown  in 
Fig.  31 — 2.  In  this  operation  the  object  is  to  make  as  tight  a  fit  as 
possible,  and  to  so  place  the  scion  that  the  cambium  layer  or  inner 
bark  will  come  into  contact  with  that  of  the  stock  at  as  many  points 
and  as  closely  as  possible.  It  will  be  seen  in  the  illustration  that  in 
thitf  method  of  grafting,  the  cambium  of  the  stock  and  scion  may  be  in 
contact  upon  at  least  three  different  surfaces.  The  grafter  should 
carry  along  a  whetstone  and  keep  his  knife  blade  clean  and  razor-sharp 
at  all  times. 

After  placing  the  scion  upon  the  stock  the  next  operation  is  that 
of  tying.  This  consists  in  wrapping  soft  cotton  twine  or  raffia  fibre 
tightly  about  the  union  of  stock  and  scion  in  such  a  way  as  to  hold 
them  firmly  together.  If  raffia  is  used,  it  should  be  soaked  in  water 
to  make  it  more  pliable. 

The  next  operation  is  that  of  waxing,  which  consists  in  thoroughly 
painting  over  the  stock  and  scion  in  the  vicinity  of  the  union  and  also 
the  upper  end  of  the  scion  wTith  grafting  wax.  It  is  better  to  leave  a 
narrow  strip  on  the  back  of  the  stock  unwaxed  in  order  that  the  raffia 
or  twine  used  for  tying  may  decay  more  readily,  or  may,  if  necessary, 
be  cut  at  this  point.  With  twine  it  is  especially  necessary  to  cut  and 
loosen  it  after  growth  from  the  scion  is  well  started. 

Various  formulas  for  preparing  the  wax  are  in  use,  but  all  usually 
consist  essentially  in  a  combination  of  beeswax  and  resin  in  various 
proportions,  to  which  a  little  oil  or  paraffine  is  added,  together  with 
other  substances  in  some  cases.     The  following  formula  is  a  good  one : 

Resin     4  pounds. 

Beeswax    1  pound. 

Linseed    oil    1  pint. 

The  resin  and  beeswax  are  melted  in  a  kettle  and  thoroughly  mixed 
with  the  oil  while  in  a  liquid  condition.  Some  use  raw  and  some 
boiled  oil.     The  former  sometimes  foams  up  to  a  troublesome  extent 


222  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

in  boiling.  The  formula  may  be  varied  by  using  as  much  as  10  or 
as  little  as  2  pounds  of  resin  to  the  pound  of  beeswax,  according  to  the 
desired  consistency  of  the  wax.  The  greater  proportion  of  resin  the 
harder  will  be  the  wax,  and  vice  versa.  Harder  wax  is  necessary  in 
hot  weather,  as  it  should  not  be  soft  enough  to  melt  and  run.  This 
is  less  likely  to  occur  in  nursery  than  in  top  grafting.  If  too  much 
resin  is  used,  the  wax  is  then  hard  and  brittle.  Kesin  is  much  cheaper 
than  beeswax,  and  in  nursery  work  may  usually  be  used  in  the  larger 
proportions  mentioned.  One  half  pound  of  tallow  may  be  substituted 
for  the  pint  of  oil.  In  some  cases  one  pound  of  flour  or  one  to  two 
pounds  of  powdered  charcoal  is  added  to  the  formula  and  thoroughly 
mixed  in,  with  the  idea  of  giving  the  wax  more  body  and  elasticity. 
Some  have  substituted  paraffine  for  part  of  the  beeswax  in  nursery 
grafting.  This  is  much  cheaper.  The  wax  requires  heat  in  order  to 
keep  it  in  a  liquid  condition,  which  may  be  supplied  by  means  of  a 
small  fire,  or  more  conveniently,  by  such  an  arrangement  as  that  shown 
in  Fig.  31 — 3.  This  consists  of  a  coal-oil  can  with  a  round  hole  in  the 
side,  over  which  a  disk  of  tin  is  fastened  in  such  a  manner  that  it  may  be 
raised  or  lowered  for  a  door.  In  the  bottom  of  this  can  is  placed  a 
small  oil  stove  on  which  is  set  the  pot  of  wax.  A  handle  at  the  top  com- 
pletes the  apparatus,  which,  while  crude,  is  very  satisfactory.  Another 
very  good  device  is  that  used  by  plumbers  for  keeping  a  pot  of  solder 
in  a  melted  condition. 

After  thorough  waxing,  in  which  no  cut  portion  of  the  stock  or  scion 
should  be  left  uncovered,  the  dirt  should  be  hoed  back  again  about 
the  newly  grafted  trees,  covering  scion  and  bud  completely  with  soil. 
This  must  be  done  very  carefully,  in  order  not  to  displace  or  knock  out 
the  scions,  and  the  dirt  should  be  worked  up  as  fine  as  possible  with 
the  hoe  and  all  hard  lumps  and  rocks  removed.  This  is  a  consideration 
to  be  kept  in  mind  in  choosing  soil  for  a  walnut  nursery,  as  the  success 
of  grafting  by  this  method  depends  quite  largely  on  thorough  cover- 
ing of  the  grafts  with  loose  soil. 

In  grafting  by  this  method  on  a  large  scale  several  men  can  work 
in  combination  to  advantage,  rather  than  for  one  man  to  do  everything. 
It  is  of  advantage,  for  instance,  for  the  man  who  does  the  actual  graft- 
ing to  do  nothing  else  but  this,  since  otherwise  he  must  be  continually 
getting  up  and  down,  going  ahead  and  back,  and  losing  much  time. 
The  better  arrangement  is  for  one  man  to  hoe  the  dirt  away  from  the 
trees  before  they  are  cut  off,  hoe  it  back  again  after  grafting  is  com- 
pleted, and  perhaps  help  in  some  other  way  if  this  does  not  keep  him 
busy.  One  man  can  cut  off  the  seedlings  and  also  do  the  tying  and 
waxing,  first  working  on  ahead  of  the  grafters  until  he  has  cut  off 
enough  trees  to  keep  them  busy  for  some  little  time,  then  coming  back 
and  attending  to  the  grafts  which  they  have  put  in.     He  should  not  get 


Bulletin  231 J 


WALNUT    CULTURE    IN    CALIFORNIA. 


223 


too  far  behind  in  the  latter  operation,  avoiding  any  danger  of  the  grafts 
drying  out  before  they  are  tied,  waxed  and  covered. 

Many  other  methods  of  nursery  grafting  are  in  vogue,  but  as  we  have 
said,  the  one  described  is  as  good  as  any  for  the  beginner,  and  in  our 
opinion  no  other  method  is  superior  to  it.  This  style  of  grafting  has 
been  developed  and  very  successfully  practiced  for  several  years  by 
Mr.  George  Weinshank,  of  Whittier,  to  whom  credit  should  be  given  in 
this  connection. 


Fig.   32. — Grafted    trees    in    nursery,    five    months    after    grafting. 

After  grafting  the  scions  which  have  taken  will  soon  begin  to  develop 
and  along  with  them  numerous  sprouts  from  the  seedling  rootstock. 
The  latter  must  be  continually  and  very  carefully  removed  before  they 
choke  out  the  growth  of  the  scion  or  become  so  large  as  to  leave  unde- 
sirable scars  when  they  are  finally  removed.  Growth  from  the  scion 
should  be  well  started,  however,  before  any  suckering  is  done.  Sucker- 
ing  is  an  important  operation,  since  if  done  carelessly  the  graft  is  likely 
to  become  displaced  even  after  it  has  made  considerable  growth.     If 


224  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

more  than  one  bud  on  the  scion  sends  up  a  shoot  all  but  the  strongest 
one  should  be  removed  as  soon  as  its  growth  is  assured.  The  successful 
grafts  will  send  up  shoots  very  rapidly,  and  soon  these  must  be  tied  up 
to  stakes  in  order  to  prevent  their  falling  over  and  becoming  crooked  or 
pulling  out  the  scion.  If  a  scion  sends  up  more  than  one  sprout  only 
the  best  one  should  be  allowed  to  grow.  For  tying  up  stakes  at  least  six 
feet  in  length  should  be  used,  employing  either  ordinary  lath  of  this 
length  or  1  by  1  strips,  which  are  very  satisfactory.  The  stakes  should 
be  driven  in  a  perfectly  upright  position  as  close  to  the  sprout  as  pos- 
sible and  the  latter  should  then  be  tied  to  the  stake  at  least  two  points 
in  its  length  with  large  soft  twine  or  small  rope.  This  tying  should  be 
done  carefully  and  not  too  tightly,  as  the  young  sprouts  are  very  tender 
and  increase  rapidly  in  diameter. 

Meantime,  proper  care  should  be  given  to  the  soil  by  means  of  the 
necessary  cultivation,  hoeing,  and  irrigation  if  the  latter  is  practiced. 
Here,  again,  there  is  a  common  impression  that  trees  grown  without  irri- 
gation are  hardier  and  more  desirable  for  planting  than  those  to  which 
water  is  applied  during  their  growth.  It  is  true  that  a  non-irrigated 
tree  becomes  dormant  earlier  in  the  season  and  hardens  up  its  terminal 
growth  possibly  more  completely  than  does  a  tree  which  is  kept  growing 
by  irrigation  as  late  in  the  fall  as  possible.  Even  though  this  is  true, 
the  fact  still  remains  that  the  largest  trees  are  everywhere  considered 
most  desirable  for  planting,  and  the  price  received  by  the  nurserymen 
varies  in  direct  proportion  to  the  size  of  the  trees.  A  tree  ten  feet  high 
sells  commonly  for  nearly  twice  as  much  as  one  four  feet  high,  and  is  at 
the  same  time  more  in  demand.  If  properly  treated  in  planting,  the 
larger  tree  is  cut  back  in  any  event  to  perfectly  sound,  well  formed 
wood,  and  we  know  therefore  of  no  disadvantage,  either  theoretically  or 
in  actual  experience,  in  the  planting  of  larger  trees  which  result  from 
irrigation  as  compared  to  that  of  small  trees  grown  without  water.  In 
fact,  many  trees  grown  where  no  irrigation  is  possible  have  their  roots 
injured,  their  growth  stunted  and  their  trunks  sunburned  on  account  of 
drouth. 

If  grown  with  plenty  of  moisture  and  on  good  soil,  the  majority  of 
the  trees  should  make  sufficient  growth  the  first  year  to  bring  them 
up  to  proper  size  for  selling  and  planting  in  orchard  form.  In  the 
southern  part  of  the  State,  where  the  season  is  long,  there  is  as  much 
trouble  from  the  trees  becoming  too  large  as  in  their  being  too  small  at 
the  end  of  the  first  season's  growth.  Trees  of  ten  to  twelve  feet  in 
height  are  very  common,  while  the  largest  specimens  run  up  to  fifteen  or 
even  eighteen  feet  during  the  first  season  from  the  graft.  There  is 
always  a  considerable  variation  in  the  trees,  however,  and  nurserymen 
commonly  sell  walnut  trees  on  the  basis  of  height,  making  the  following 
grades :    4  to  6  feet,  6  to  8  feet,  8  to  10  feet,  and  10  feet  and  up.      A 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  225 

grafted  tree  of  less  than  four  feet  in  height  at  the  end  of  the  first  season, 
when  grown  among  trees  some  of  which  go  up  to  ten,  twelve  and  more 
feet,  is  of  doubtful  value,  as  it  should  presumably  have  made  a  better 
growth  if  on  a  good  root  and  with  a  good  union. 

From  the  seedlings  where  the  grafts  did  not  take,  numerous  suckers 
usually  spring  up  and  it  is  customary  to  take  off  all  but  one  of  these, 
letting  the  latter  grow  up  into  a  new  seedling  top.  This  will  soon  grow 
over  the  scar  where  the  original  top  was  cut  off  and  may  be  grafted 
again  the  next  year  if  this  seems  desirable.  It  is  not,  however,  to  be 
recommended  that  such  trees  be  grafted  again  and  again  the  third  and 
even  the  fourth  year,  as  practiced  by  some  nurserymen  in  case  the  grafts 
do  not  take.  In  such  cases  the  root  becomes  extremely  large,  and  with 
each  year's  cutting  off  of  the  top  the  scar  at  the  base  becomes  greater. 
It  is  better  to  discontinue  grafting  after  the  second  year  and  destroy 
all  the  remaining  seedlings  on  which  the  graft  has  not  taken.  By  far 
the  most  desirable  grafted  tree  consists  of  a  two-year-old  root  and  one- 
year-old  top,  as  described  above.  Thus  the  top  and  root  are  of  nearly 
uniform  size,  and,  if  a  good  union  is  formed,  complete  healing  at  the 
point  of  grafting  takes  place  the  first  season. 

BUDDING. 

The  operation  of  budding  the  walnut  is  by  no  means  as  uniformly 
successful  as  in  the  case  of  ordinary  fruit  trees,  yet  some  have  per- 
formed it  with  considerable  success.  Even  at  best,  results  in  this 
respect  have  been  somewhat  uncertain.  Many  different  methods  have 
been  practiced,  but  these  we  will  not  go  into  in  detail,  as  they  are  largely 
a  matter  of  personal  skill  and  there  is  no  reason  for  supposing  one 
method  to  be  better  than  the  others  under  all  conditions.  In  general, 
we  may  say  that  most  of  the  walnut  budding  in  this  State  has  been  done 
in  the  fall,  usually  in  September^  the  buds  remaining  dormant  over 
winter  and  starting  into  growth  the  following  spring.  In  some  of  our 
own  experience,  however,  we  have  had  good  results  with  spring  budding, 
putting  in  the  buds  during  May,  June  and  early  July  and  growing  from 
them  trees  up  to  as  much  as  ten  feet  in  height  during  the  same  season. 
Spring  buds  of  this  height  are  exceptional,  but  we  have  found  no  diffi- 
culty in  getting  a  large  percentage  of  them  up  to  from  four  to  six  feet 
during  the  same  summer  when  they  were  budded.  Such  budding  was 
done  mostly  on  new  sprouts  coming  from  one-year-old  seedlings  upon 
which  grafts  had  failed,  or  seedlings  which  had  been  too  small  to  graft 
during  the  previous  winter.  For  such  work  the  best  buds  are  those 
upon  dormant  wood  cut  during  the  previous  winter  at  the  same  time  of 
cutting  scions  for  grafting.  Such  wood  may  be  easily  kept  over  with 
the  buds  dormant  until  June  if  properly  stored  in  a  cool  place  with 
neither  too  much  nor  too  little  moisture.  The  buds  on  this  grafting 
8—231 


226 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


wood  do  not  come  off  readily  when  the  scions  are  first  cut,  but  when 
budding  time  arrives  in  the  spring  the  scions,  if  well  kept,  will  begin  to 
callous  at  the  ends,  and  the  buds  will  then  slip  off  readily.  Wood  which 
is  too  large,  and  also  that  which  is  too  soft  and  pithy  for  scions,  can  be 
used  for  buds,  and  thus  it  is  possible  to  make  considerable  more  use  of  a 
given  amount  of  grafting  wood.  Buds  of  the  current  season  may  also 
be  used,  and  for  fall  work  it  is  necessary  to  use  such  buds.  We  have 
found  that  these  can  be  handled  most  readily,  by  selecting  the  best 


Fig.  33. — Top-budding;  1,  bud  completely  healed  and  starting  to  grow;  2,  showing 
the  shoot  developed  from  the  bud  and  tied  up  to  the  stub  of  the  limb.  The  latter 
is  soon  cut  off  just  above  the  bud.  The  ring  of  bark  attached  to  the  bud  would 
be  better  if  it  reached  less  completely  around  the  limb.  Note  the  constriction  at 
the  bud  and  swelling  above  it. 

developed  buds  at  the  base  of  leaves  on  the  oldest  wood  of  the  present 
season's  growth,  and  cutting  off  the  leaf  stalks  just  beyond  the  buds 
about  two  weeks  previous  to  the  desired  time  of  budding.  If  this  be 
done  the  leaf  stalks  drop  off  cleanly  in  a  few  days,  leaving  the  buds 
ready  for  use.  If  the  leaves  are  cut  too  soon  the  buds  sometimes  start 
into  growth  while  still  on  the  parent  shoot.  Good  buds  may  sometimes 
be  obtained  during  the  summer  and  fall  on  the  last  wood  of  the  previous 
year's  growth. 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  227 

The  most  successful  form  of  bud  with  us  has  been  a  partial  ring  or 
flute  bud  extending  only  part  way  round  the  stem.  We  have  had  the 
best  success  with  buds  having  a  portion  of  bark  attached  about  one  half 
to  three  quarters  of  an  inch  wide  and  three  quarters  of  an  inch  long. 
The  former  dimension  is  that  measured  around  the  stem  and  the  latter 
the  vertical  distance.  For  cutting  and  placing  such  buds  a  double- 
bladed  knife  is  most  suitable  for  which  we  have  found  a  home-made 
contrivance  entirely  satisfactory.  Two  blades  are  fixed  upon  a  handle  in 
such  a  manner  that  they  are  about  three  quarters  of  an  inch  apart. 
With  this  cuts  are  made  on  either  side  of  the  bud  on  the  bud  stick,  after 
which  similar  cuts  are  made  in  the  bark  of  the  stock  about  six  inches 
above  ground  if  the  seedling  is  large  enough.  These  cuts  should  not 
extend  more  than  halfway  round  the  tree,  leaving  the  bark  intact  for 
halfway  round  on  the  other  side.  Referring  to  the  sentence  above,  where 
we  state  the  proper  size  of  the  piece  of  bark  attached  to  the  bud,  it  will 
be  seen  that  the  buds  should  be  put  on  at  a  place  where  one  half  the  cir- 
cumference of  the  stock  amounts  to  at  least  one  half  to  three  fourths  of 
an  inch.  Perpendicular  cuts  are  then  made  with  one  of  the  knife  blades 
at  either  end  of  the  ring  of  bark  on  the  stock  and  this  is  removed.  The 
bud,  previously  cut,  is  then  removed,  cut  off  if  necessary  to  the  proper 
horizontal  width,  so  that  it  will  just  fit  the  opening  in  the  bark  of  the 
stock.  In  stripping  off  the  bud  the  core  of  wood  inside  the  bud  itself 
usually  remains  in  place  without  difficulty  if  the  bud  is  mature  enough 
to  be  worth  using.  Usually  buds  in  which  the  heart  wood  pulls  out  are 
so  immature  that  they  would  not  take  in  any  event.  With  good  buds  it 
is  simply  necessary  to  strip  off  the  bark  without  attempting  to  include 
any  of  the  wood.  The  operator  uses  his  judgment  in  selecting  the  seed- 
lings of  such  a  size  that  the  strip  of  bark  bearing  the  bud,  with  its  one 
half  to  three  quarters  of  an  inch  horizontal  width,  will  be  of  the  right 
size  to  extend  not  more  than  halfway  round  the  stock.  Where  the  bud 
reaches  nearly  or  quite  around  the  stock,  forming  a  more  or  less  complete 
ring  bud,  a  bad  constriction  and  swelling  is  often  produced  at  this  point, 
making  an  undesirable  sort  of  tree.  The  bud  may  be  put  in  just  above 
ground,  or  at  any  other  point  where  the  stock  has  the  proper  size,  as 
well  as  at  six  inches  from  the  ground,  as  above  stated.  The  object  of 
the  latter  is  to  leave  space  for  further  attempts  below  the  first  bud  in 
case  it  does  not  take.  The  bud  is  slipped  into  place  and  tied  either  with 
waxed  cloth,  such  as  is  used  in  budding  citrus  seedlings,  or  with  soft 
cotton  budding  twine.  We  have  had  the  most  uniform  success  with 
waxed  cloth.  The  tying  should  be  done  very  carefully,  bringing  the 
inner  surface  of  the  bud  bark  into  smooth,  close  contact  with  the  exposed 
wood  of  the  stock,  especially  close  about  the  bud  itself.  After  securing 
the  buds  in  place  they  should  be  watched  carefully  and  if  successful 
they  will  remain  green  and  soon  unite  with  the  stock.     Spring  buds  may 


228  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

usually  be  unwrapped  within  from  one  to  two  weeks,  the  latter  period 
being  usually  about  right  early  in  the  season.  In  later  budding  the 
wrapping  must  stay  on  longer,  usually  at  least  three  weeks  in  July, 
while  with  fall  buds  which  are  to  remain  dormant  over  winter  six  or 
seven  weeks  will  do  no  harm.  With  spring  or  summer  buds  which  are 
to  be  forced  into  growth  the  same  season  about  one  third  to  one  half  of 
the  seedling  top  should  be  cut  off  after  the  buds  are  unwrapped.  After 
the  bud  has  started  into  growth  and  its  further  development  is  assured, 
the  stock  should  be  still  further  cut  back  as  closely  as  possible  to  the  bud 
without  injuring  it  and  the  end  waxed  over.  In  the  case  of  fall  buds 
which  are  to  remain  dormant  over  winter  the  seedling  top  should  not  be 
cut  off  at  all  until  spring,  when  it  may  be  cut  off  entirely  at  one  time  if 
the  growth  of  the  bud  commences  vigorously  early  in  the  season,  or  if  the 
bud  does  not  start  promptly  it  may  be  safer  to  cut  off  only  one  half  of 
the  top  and  the  remainder  after  the  bud  commences  to  grow. 

This  form  of  bud  is  shown  on  a  top-worked  tree  in  Fig.  33.  The  buds 
in  the  figure,  however,  extend  further  around  the  stem  than  we  now 
think  desirable.  A  bud  which  does  not  reach  more  than  halfway  round 
does  not  produce  the  swelling  and  constriction  of  the  stock  seen  in  these 
pictures. 

Other  methods  than  the  above  have  been  tried  for  budding  walnuts 
and  some  have  given  more  or  less  success  both  with  us  and  others.  The 
ordinary  shield  bud  has  been  entirely  unsuccessful  in  our  experience, 
and  it  seems  to  a  certain  extent  that  the  larger  the  portion  of  bark  taken 
off  with  the  bud  the  better  are  its  chances  to  stick.  Some  who  have  used 
an  inverted  shield  or  T  bud,  pushing  the  bud  up  rather  than  down  and 
slipping  it  under  the  bark,  have  had  better  success  than  by  the  ordinary 
method  of  making  this  bud.  Complete  ring  or  annular  buds  take  as 
readily  as  the  flute  bud  described  above,  but  there  is  objection  to  this 
form  on  account  of  the  constriction  produced  in  the  stock  at  the  point 
of  budding.  "Where  a  strip  of  bark  is  left  on  the  back  side  of  the  stock, 
as  in  the  flute  bud  which  we  have  described,  this  objection  is  obviated. 

E.  J.  Kraus,  in  Circular  Bulletin  No.  16  of  the  Oregon  Agricultural 
Experiment  Station,  recommends  what  he  calls  a  hinge  bud,  which  is 
a  large,  rectangular  patch  bud  inserted  under  the  bark  of  the  stock. 
In  this  form  of  budding  two  transverse  cuts  are  made  in  the  bark,  one 
above  the  other,  about  half  an  inch  long  and  three  quarters  of  an  inch 
apart.  The  two  are  connected  in  the  center  with  a  longitudinal  inci- 
sion and  the  bud,  after  being  cut  with  a  portion  of  attached  bark  of 
the  proper  size  and  shape,  is  slipped  down  under  the  bark  of  the  stock 
in  the  same  way  as  in  the  ordinary  shield  or  T  bud. 

The  uncertain  results  which  almost  always  accompany  walnut  bud- 
ding, even  at  the  best,  appear  to  come  about  largely  on  account  of  the 


Bulletin  231]  WALNUT   CULTURE   IN   CALIFORNIA.  229 

tendency  of  the  freshly  exposed  tissue  of  the  walnut  to  oxidize  and 
turn  black.  After  this  has  once  happened  the  tissue  is  sure  to  die  and 
no  union  takes  place.  A  further  uncertainty  is  connected  with  the 
growth  of  the  bud  even  after  it  has  apparently  formed  a  perfect  union. 
Quite  frequently  a  good  union  seems  to  have  taken  place,  the  bark  of 
the  bud  remaining  fresh  and  green,  but  after  this  the  bud  dies  and 
therefore  no  sprout  is  able  to  develop.  In  all  walnut  budding  partic- 
ular skill  and  dexterity  is  necessary  in  order  that  the  fresh  surfaces  or 
cambium  of  the  bud  and  stock  may  be  exposed  as  little  as  possible  to 
the  air  during  the  operation.  The  operator  must  work  rapidly  and  at 
the  same  time  carefully,  making  a  close  fit  in  each  case,  tying  each  bud 
so  that  the  inner  surface  of  the  bark  will  come  into  close  contact  all 
over  the  exposed  surface  of  the  cut  in  the  stock,  and  getting  the  buds 
cut  and  into  place  just  as  quickly  as  possible  without  unnecessary  expo- 
sure to  the  air.  The  buds  should  not  be  taken  off  until  the  last  possi- 
ble moment  so  that  only  one  bud  can  be  cut  at  a  time.  In  working  with 
a  single-bladed  knife,  it  is  usually  necessary  to  cut  the  bud  first  and 
then  lay  it  on  the  stock  in  order  to  make  the  cut  on  the  latter  of  the 
same  size.  By  using  a  double-bladed  knife  this  becomes  unnecessary, 
and  the  bark  can  be  removed  from  the  stock  before  the  bud  is  entirely 
removed.  In  case  of  any  little  delay  after  cutting  the  bud  it  is  a  good 
idea  for  the  operator  to  put  the  bud  in  his  mouth  until  he  is  ready  to 
place  it  upon  the  stock,  rather  than  to  keep  it  exposed  to  the  air.  In 
nursery  budding  on  a  large  scale  it  may  be  found  economical  for  the 
men  to  work  in  pairs  rather  than  for  each  man  to  do  all  the  work.  One 
man,  for  instance,  may  make  the  cut  on  the  stock,  cut  and  place  the 
bud,  while  the  other  ties,  waxes  or  otherwise  assists  to  the  best  advan- 
tage. There  should  not  be  the  slightest  delay,  however,  at  any  stage 
of  the  operation. 

As  a  general  proposition,  there  are  but  few  advantages  in  nursery 
budding  over  grafting  for  one  who  is  particularly  skilful  in  the  latter 
operation.  Grafting  can  be  done  more  rapidly,  and  is  certain  to  pro- 
duce good-sized  trees  the  same  year  if  they  are  well  cared  for.  Bud- 
ding, however,  may  be  valuable  at  times,  especially  if  practiced  in  con- 
junction with  grafting.  In  the  case  of  propagating  varieties  where 
grafting  wood  is  scarce,  the  available  supply  goes  considerably  further 
in  budding  than  in  grafting,  since  only  one  bud  is  used  for  each  tree 
and  buds  can  be  taken  from  soft,  pithy  wood,  or  large  wood  which 
would  not  make  a  scion.  Another  useful  feature  of  budding  is  that  it 
may  be  practiced  in  spring  and  early  summer  upon  trees  which  were 
too  small  for  grafting,  or  upon  the  sprouts  coming  from  trees  on  which 
grafts  did  not  take.  It  also  extends  for  several  weeks  the  rather  lim- 
ited season  during  which  grafting  may  be  done.     Another  advantage 


230  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

of  budding  lies  in  the  fact  that  very  little  suckering  has  to  be  done, 
such  as  is  necessary  after  grafting,  and  this  is  a  valuable  consideration. 
Again,  the  budded  tree,  having  the  union  well  above  ground,  is  not 
as  liable  to  decay  or  heal  poorly  at  this  point  as  is  the  graft.  Both 
operations  may  often  be  practiced  to  advantage  by  the  nurseryman, 
grafting  in  February  and  March  all  the  stocks  which  are  large  enough, 
budding  in  April  and  May  those  which  were  too  small  for  grafting,  and 
in  June  and  in  early  July  the  sprouts  which  have  come  up  from  the 
unsuccessfully  grafted  trees.  By  budding  several  inches  from  the 
ground  those  seedlings  which  do  not  take  can  be  budded  again  a  little 
lower  down,  and  thus  by  diligent  and  continuous  work  it  is  not  impos- 
sible to  obtain  a  nearly  perfect  stand  of  salable  trees  during  the  first 
year.  Fall  budding  upon  stocks  in  their  second  year  of  growth  pro- 
duces very  large  trees  the  following  year,  and  so  is  of  some  advantage. 
With  very  thrifty  seedlings  it  is  possible  to  do  a  good  deal  of  budding 
during  the  late  summer  and  fall  of  the  same  year  in  which  the  nuts 
were  planted,  and  this  again  may  sometimes  be  of  advantage  in  obtain- 
ing a  long  season  during  which  the  stock  may  be  worked.  Inquiry  is 
sometimes  made  as  to  the  possibility  of  producing  salable  trees  in  one 
year  by  sprouting  nuts  early,  forcing  their  growth  in  the  nursery  so 
that  they  may  be  budded  in  June  or  early  July  of  the  same  year,  and 
then  pushing  the  sprout  along  to  make  a  tree  that  same  season.  While 
this  is  possible  with  peach  and  other  fruit  trees,  it  is  not  likely  that 
it  can  be  accomplished  with  walnuts  to  any  extent  or  that  the  green, 
immature  buds  thus  produced  would  have  any  ultimate  advantage  in 
orchard  planting.  The  future  care  of  buds  is  the  same  as  that  of  grafts 
and  need  not  be  particularly  described. 

METHODS  OF  TOP-WORKING. 

In  working  over  good-sized  walnut  trees,  either  in  the  ease  of  black 
walnuts  planted  in  orchard  form,  black  walnuts  standing  along  road- 
sides, in  dooryards,  or  any  other  place  where  it  is  desired  to  work  them 
over  into  English  walnuts,  or  in  the  case  of  English  walnuts  which  the 
owner  wishes  to  change  over  into  other  varieties,  somewhat  different 
methods  are  usually  employed  than  those  used  in  nursery  work. 

Top-Grafting. — In  regard  to  the  time  of  grafting,  choice  and  care  of 
the  scions,  making  of  grafting  wax,  and  other  operations  common  to 
both  processes,  the  same  general  rules  apply.  Trees  to  be  worked  over 
may  be  cut  off  either  in  the  main  stem  from  two  to  five  feet  above 
ground,  if  this  is  at  least  3  to  4  inches  in  diameter,  or  the  limbs  may 
be  cut  off  and  grafted  either  just  above  the  main  forks  of  the  tree  or 
further  out,  according  to  the  size  of  the  limbs  and  the  amount  of  graft- 
ing wood  available.     It  is  not  usually  advisable  to  cut  off  extremely 


Bulletin  231] 


WALNUT    CULTURE   IN    CALIFORNIA. 


231 


large  limbs,  exposing  a  large  surface  of  wood  to  decay  and  also  making 
the  growth  of  the  scions  somewhat  less  certain  than  if  they  are  inserted 
in  smaller  limbs.  Usually  cuts  of  3  or  4  inches  in  diameter  are  the 
most  desirable  size,  although  larger  and  also  smaller  cuts  can  be  grafted 
with  more  or  less  success.  In  grafting  over  orchard-planted  black  wal- 
nut trees  it  is  not  usually  advisable  to  graft  them  before  they  have  a 
diameter  of  at  least  3  inches  at  the  point  of  grafting,  and  4  inches  is 


Fig.   34. — Views  of  four  different  sides  of  scion  for  top-grafting  by  side  cleft  method. 

even  better.  If  the  trees  are  grafted  while  quite  small,  the  tops  are 
likely  to  greatly  outgrow  the  trunk  and  form  a  topheavy,  undesirable 
form  of  tree.  In  working  over  trees  in  the  top  less  time  and  fewer 
scions  are  required  if  the  limbs  are  cut  well  back  toward  the  main  forks, 
making  fewer  stubs  to  work  upon,  than  if  the  limbs  are  cut  off  further 
out  where  the  branches  are  more  numerous.  In  the  latter  case,  how- 
ever, the  chances  of  success  are  somewhat  better  than  when  the  work 


232 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 


is  done  on  very  large  stubs.     Usually  cuts  of  less  than  2  or  more  than 
4  inches  diameter  are  undesirable. 

A  method  used  in  some  cases  is  that  of  cutting  off  the  tops  quite 


Fig.   35. — Top-grafting.      Bottom — Making    the    cleft.      Top — Scions    inserted    and    waxed. 

severely  one  year  and  then  allowing  the  stubs  to  sprout,  which  they 
usually  do  very  vigorously,  and  grafting  on  the  best  of  these  young 
sprouts  the  following  year.     In  following  this  method  some  have  cut 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  233 

off  trees  a  foot  or  more  in  diameter  directly  through  the  main  trunk 
and  then  worked  the  following  year  on  the  sprouts  coming  from  this. 
Such  a  method  is  of  doubtful  expediency  on  account  of  the  great 
liability  to  decay  of  so  large  a  cut  surface. 

The  time  chosen  for  cutting  off  the  top  or  limbs  for  top-grafting  is 
usually  that  when  the  grafting  is  done,  namely,  just  before  the  trees 
commence  to  send  out  new  growth  in  the  spring.  One  of  the  most  im- 
portant considerations  in  this  respect  is  that  of  the  bleeding  of  the 
trees  when  cut  off,  which  sometimes  takes  place  quite  profusely.  No 
general  statement  can  be  made  as  to  the  time  or  conditions  under  which 
such  bleeding  takes  place,  or  does  not  take  place,  since  its  occurrence 
is  quite  irregular.  In  some  soils,  especially  light  sandy  ones,  and  in 
some  seasons  it  seems  almost  impossible  to  find  a  time  when  the  trees 
can  be  cut  off  without  bleeding.  We  have  seen  practiced  a  method  of 
cutting  off  the  tops  and  branches  early  in  the  winter,  in  December  for 
instance,  when  there  is  practically  no  danger  of  bleeding,  and  then  at 
the  time  of  grafting  making  a  fresh  cut  just  back  into  normally  green 
tissue.  In  this  way  some  who  have  had  trouble  with  bleeding  have 
thought  that  much  benefit  was  obtained.  Another  method  consists  in 
cutting  off  the  tops  just  before  grafting  and  then,  if  bleeding  takes 
place,  boring  several  half -inch  holes  in  the  butt  of  the  tree  near  the 
ground  in  order  to  allow  the  surplus  sap  to  escape  at  that  point.  Usually 
the  tops  may  be  cut  off  at  the  proper  time  for  grafting  without  any 
serious  trouble  from  bleeding  except  now  and  then  in  certain  individual 
trees,  or  sometimes  in  certain  individual  orchards  on  an  especially  warm 
soil.  The  cuts  should  be  made  carefully  in  order  not  to  split  and  tear 
down  the  stubs.  The  best  method  consists  in  first  making  a  cut  on  the 
under  side  in  the  case  of  a  horizontal  limb,  or  cutting  partially  through 
on  one  side  in  the  case  of  a  tree  cut  off  in  the  trunk,  then  cutting  com- 
pletely through  on  the  other  side  an  inch  or  two  above  the  first  cut. 
After  taking  off  the  limb  or  top  a  fresh  cut  is  made  clear  across,  just 
below  the  first  cuts,  in  sound  wood. 

The  question  sometimes  arises,  especially  in  working  over  good-sized 
or  large  trees,  whether  to  cut  off  all  the  limbs  at  one  time  or  to  work 
over  only  part  of  the  top  the  first  year,  leaving  part  of  the  original 
branches  over  until  the  second  or  even  later  years,  thus  extending  the 
grafting  over  two  or  more  years.  Most  experience  has  been  against 
the  latter  method  and  in  favor  of  cutting  off  and  grafting  the  whole 
top  at  one  time,  even  with  the  largest  trees.  Ordinarily,  if  part  of  the 
original  top  is  left,  very  little  growth  results  from  the  scions,  the  whole 
vigor  of  the  tree  seeming  to  go  into  the  remaining  portion  of  the  original 
top.  We  have  heard  the  plan  proposed  of  grafting  the  north  side  of 
the  tree  first,  then  the  east,  south  and  west  in  successive  years,  this 
idea  being  based  on  the  well-established  observation  that  grafting  is 


234 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


decidedly  more  successful  on  the  north  than  on  the  south  side  of  the 
tree.  We  do  not  know  that  this  method  has  been  tried  sufficiently  to 
enable  final  judgment  to  be  passed  upon  it,  but  certainly  with  trees  of 


Fig.   36. — Top-grafting;    scion    inserted. 


not  extremely  large  size  and  especially  in  grafting  over  orchard-planted 
black  walnut  trees,  it  is  more  practical  to  cut  off  the  whole  top,  either 
in  the  trunk  or  main  forks,  and  graft  it  all  at  once. 

The  method  used  in  top-grafting  is  usually  the  ordinary  cleft  graft 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  235 

or  a  modification  of  the  same.  Some  operators  simply  split  the  stock 
through  the  middle,  insert  the  wedge  in  the  cleft,  trim  the  split  edges 
of  the  bark  and  cambium  smoothly  with  a  sharp  knife,  cut  the  scion 
to  a  smooth  bevel  on  either  side,  and  insert  the  same  carefully,  taking 
special  pains  to  make  a  good  fit  and  bring  the  cambium  layers  of  the 
stock  and  scions  into  intimate  contact.  After  removing  the  wedge  some 
grafters  fill  the  cavity  across  the  heart  of  the  stub  with  paper  or  some 
other  material  before  waxing.  Another,  and  in  our  opinion  somewhat 
better  method  of  cleft-grafting,  especially  on  stubs  more  than  two 
inches  in  diameter,  is  that  shown  in  Fig.  35.  This  differs  from  the 
ordinary  method  in  that  instead  of  making  one  cleft  across  the  middle 
of  the  stub  two  or  more  are  made  at  uniform  distances  apart  out 
near  the  edge,  splitting  off  slabs  about  one  half  an  inch  in  thickness. 
A  special  tool  is  useful  both  for  this  or  for  ordinary  cleft-grafting,  as 
shown  in  Fig.  35.  In  making  the  splits  the  splitting  wedge  is  held 
in  a  horizontal  position  over  the  place  where  the  cleft  is  desired  and 
driven  in  to  a  depth  of  about  one  half  inch.  It  is  then  tilted  up  in  a 
slanting  position  and  driven  down  to  a  depth  of  one  and  a  half  to  two 
inches,  first  at  one  end  of  the  cut  and  then  at  the  other.  The  limb  in 
Fig.  35  was  3J  inches  in  diameter.  In  this  two  clefts  were  made, 
each  -J  inch  thick  by  2\  inches  long  and  2  inches  deep.  The  rough 
edges  of  the  bark  were  smoothed  with  a  sharp  knife  and  the  cleft  held 
open  with  the  terminal  portion  of  the  tool,  as  shown  in  Fig.  36.  The 
proper  scion  for  such  grafting  is  shown  in  Fig.  34.  This  is  prepared 
by  beveling  off  one  end  into  a  wedge  shape,  cutting  entirely  through 
the  pith  on  one  side,  and  then  down  to  the  pith  on  the  other.  The  back 
side  of  the  wedge,  that  which  is  placed  toward  the  outside  of  the  tree, 
is  made  wider  than  the  side  which  goes  toward  the  interior  of  the  tree. 
There  should  be  two  buds  on  each  scion,  one  near  each  end  as  shown 
in  the  illustration.  Two  scions  are  carefully  fitted  into  each  cleft, 
taking  great  pains  to  make  a  good  fit  and  bring  the  cambium  portions 
of  stock  and  scion  into  intimate  contact.  If  the  bark  splits  irregularly 
it  should  be  smoothed  with  a  sharp  knife.  In  all  cleft  grafting  it  is 
well  to  slant  the  point  of  the  scion  a  little  toward  the  center  of  the 
stock  so  that  the  upper  end  of  the  scion  points  out  a  little  in  order  to 
be  certain  that  the  cambium  may  cross  at  least  at  one  point.  In 
grafting  limbs  up  to  4  inches  in  diameter  two  clefts  or  four  scions 
are  commonly  put  in  by  this  method.  In  larger  limbs  more  clefts  and 
scions  may  be  used.  It  is  desirable  to  put  in  as  many  scions  as  possible 
without  at  the  same  time  splitting  off  slabs  of  too  little  thickness,  since 
the  more  scions  that  grow  the  quicker  will  the  cut  surface  heal  over. 
It  is  much  better  to  get  several  scions  started,  even  though  it  be  neces- 
sary to  cut  off  all  but  one  the  following  year  rather  than  having  only 


236 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


one  scion  from  the  first  with  a  large  surface  exposed  to  decay.  After 
inserting  the  scions  and  removing  the  wedge  the  scions  may  be  tied  in 
with  soft  budding  twine,  wrapped  several  times  around  the  whole  stub, 


Fig.   37. — Large,  top-grafted  tree.     J.  B.  Neff's  orchard. 

but  this  is  not  ordinarily  very  necessary.     Only  in  cases  where  the 
work  is  being  done  with  extreme  care  is  tying  often  resorted  to. 

One  of  the  most  important  operations  of  the  whole  process  is  that  of 


Bulletin   231] 


WALXUT    CULTURE    IN    CALIFORNIA. 


237 


waxing.  Grafting  wax  should  be  prepared  as  described  on  page  221,  and 
every  part  of  the  exposed  surface  should  be  very  carefully  painted  over 
with  a  solid  coating  of  wax.  Great  pains  should  be  taken  to  see  that 
no  spots  are  left,  however  small,  either  on  the  cut  end  of  the  limb  or  the 
clefts  containing  the  scions,  which  are  not  completely  covered  with  wax. 
If  any  opening  is  left  through  which  the  air  may  penetrate,  drying  and 
oxidizing  the  fresh  surfaces  of  the  scion  or  stock,  the  grafts  will  almost 


Fig.   38. — Top-grafting;    scions    starting   into    growth. 

certainly  perish.  Much  care  should  be  taken  while  waxing  not  to  knock 
out  or  disturb  the  scions  in  the  least.  One  waxing  is  not  sufficient,  but 
after  a  few  days  the  grafts  should  be  gone  over  again,  closing  carefully 
any  places  found  to  be  unwaxed.  A  little  later,  when  the  grafts  begin 
to  grow  and  swell  more  or  less,  it  will  be  found  that  the  wax  is  very 
likely  to  split  or  peel  off  and  so  they  should  be  watched  very  carefully 
until  thoroughly  united  and  kept  liberally  covered  with  wax.    The  pro- 


238  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

portion  of  resin  and  beeswax  contained  in  the  material  may  require 
variation  after  the  first  waxing.  Too  much  beeswax  makes  a  soft  wax 
which  melts  easily  in  the  sun,  running  away  from  its  proper  position, 
while  if  too  much  resin  is  used  the  resulting  wax  is  stiff  and  brittle  and 
readily  cracks.  Beeswax  is  much  more  expensive  than  resin,  and  it  is 
therefore  desirable  for  economy's  sake  to  limit  its  use. 

It  is  the  practice  of  some  grafters  to  enclose  each  stub,  after  grafting, 
with  a  large  paper  sack,  hood  or  cuff,  in  order  to  protect  the  tender 
young  sprouts  from  sun,  wind  or  frost.  As  the  sprouts  elongate  the 
paper  is  pulled  open  at  the  top  to  let  them  through.  If  the  scions  are 
tied  in  with  string  this  must  be  cut  as  soon  as  they  are  well  started  in 
order  that  it  may  not  cut  into  the  growing  scion. 

Top-grafting  at  best  is  not  always  successful,  even  with  the  most 
experienced  operators.  Much  depends  on  the  condition  of  the  tree  at 
the  time  of  grafting  in  regard  to  the  activity  of  the  sap,  and  this  cannot 
be  foretold  or  controlled  in  many  instances.  At  the  same  time  a  skillful 
operator,  especially  if  he  has  a  sufficient  choice  of  grafting  wood,  can 
in  most  cases  top-graft  the  walnut  with  fairly  uniform  results.  Even 
after  successful  grafting  has  been  done,  the  young  sprouts  coming  from 
the  scions  are  extremely  susceptible  to  injury  from  frost  and  also  from 
hot  winds,  and  failure  somtimes  results  from  these  sources. 

These  scions  which  establish  a  successful  union  soon  commence  to 
grow  after  grafting,  sending  out  sprouts  from  one  or  both  buds  which 
grow  very  rapidly,  having  at  first  a  very  tender,  delicate  nature.  At 
the  same  time,  the  tree  itself  sends  out  numerous  suckers  which  must 
be  suppressed  to  a  large  extent  in  order  to  give  the  grafts  every  oppor- 
tunity for  development.  Considerable  judgment  must  be  exercised  in 
regard  to  removing  the  suckers,  especially  in  cases  where  some  or  all  of 
the  grafts  do  not  grow.  If  the  grafting  is  entirely  unsuccessful,  some 
of  the  suckers  must  be  allowed  to  develop  in  order  to  permit  the  tree  to 
carry  on  its  normal  functions.  If  the  grafts  grow  on  some  of  the  limbs 
but  not  on  all,  it  may  be  well  to  leave  a  few  suckers  on  the  limbs  where 
the  grafts  did  not  take.  Again,  it  may  sometimes  be  better  to  leave  at 
least  one  sucker  on  a  large  limb  on  which  only  one  graft  is  growing. 
The  main  object  should  be  to  give  the  scions  every  opportunity  for  de- 
velopment without  allowing  suckers  to  choke  them  out,  while  at  the  same 
time  not  depriving  the  tree  too  much  of  an  opportunity  to  produce 
foliage.  After  grafting,  the  trunk  and  branches  of  the  trees  should  be 
painted  over  with  a  thick,  heavy  whitewash  as  a  protection  against 
sunburn.  Those  stubs  in  which  the  grafts  do  not  growT  should  be  kept 
as  carefully  waxed  as  those  where  successful  grafting  occurs,  inasmuch 
as  the  wood  is  extremely  susceptible  to  decay  and  must  be  protected 
against  the  same  as  much  as  possible. 


Bulletin  231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


239 


During  the  first  season  it  is  usually  well  to  allow  all  the  grafts  which 
grow  to  remain,  even  though  they  are  too  numerous  for  the  ultimate 
tree,  as  such  growth  causes  a  more  rapid  healing-over  of  the  cut-off 
stub  and  this  is  very  desirable.  As  soon  as  the  sprouts  begin  to  grow 
from  the  scions  preparations  must  be  made  to  support  them  in  some 
way  or  they  will  become  topheavy,  twisted  and  broken  out  by  the  wind. 
The  most  convenient  method  of  doing  this  consists  in  nailing  six-foot 
lath  directly  to  the  stubs  into  which  the  scions  were  put,  and  tying  the 


Fig.   39.*— Top-grafting  ;  growth  well  started  and  tied  up  to  lath. 

sprouts  loosely  and  firmly  to  these  laths.  In  the  case  of  orchard-planted 
black  walnuts  which  are  grafted  directly  in  the  trunk,  it  is  usually  neces- 
sary to  employ  a  large,  tall  stake  set  in  the  ground,  especially  during 
the  second  year,  as  the  tops  on  such  trees  become  extremely  large  and 
top-heavy.  This  is  one  of  the  objections  to  this  method,  as  it  is  sometimes 
almost  impossible  to  keep  the  tops  up  in  shape  during  their  early  years. 
At  the  end  of  the  first  season's  growth  top-grafted  trees  should  be 
gone  over,  the  laths  removed  if  they  seem  no  longer  necessary,  the  extra 


240 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


shoots  cut  out  where  they  are  too  numerous,  the  stubs  cut  off  and 
waxed  over  very  thoroughly  where  they  have  died  back,  and  all  sprouts 
from  the  tree  itself  either  cut  off  or  grafted  again  if  the  latter  seems 
necessary.    During  this  second  grafting  it  is  usually  better  to  work  the 


Fig.   40. — Top-grafting;  showing  growth  during  the  first  season. 

sprouts  rather  than  the  old  stubs  if  the  former  are  available.  They 
may  sometimes  be  budded  to  advantage.  Sometimes  when  no  good 
sprouts  have  developed  it  is  necessary  to  cut  the  old  stubs  off  again 
further  back  and  graft  into  them. 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA. 


241 


Fig.  41. — Top-grafting;  new  top  produced  on  a  seedling  English  walnut  tree  in  one 

season. 


9—231 


242 


UNIVERSITY    OF    CALIFORNIA  — EXPERIMENT    STATION. 


Top-Working  by  Budding. — Trees  may  sometimes  be  top-worked  to 
advantage  by  budding  rather  than  grafting,  working  on  smooth-barked 
limbs  not  much  over  one  inch  in  diameter  or  on  suckers  coming  from 
large  limbs  cut  off  the  previous  year.  The  methods  already  described 
as  to  cutting  the  tops,  treatment  of  the  stubs  and  methods  of  budding 


Fig.  42. — Top-grafting;  two  years'  growth  on  orchard-planted 
black  walnut.      Dr.  W.  W.  Fitzgerald. 


will  apply.  Fig.  33  shows  the  partial  ring  bud  after  forming  a  union 
and  the  same  with  considerable  growth  developed,  the  bud-sprout  being 
tied  up  to  the  partially  cut  off  limb.  The  ring  of  bark  on  these  buds 
extends  a  little  further  around  the  limb  than  is  desirable. 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA. 


243 


■•'"     ■•■  -  „   ■•  •■ 
aft"*     ..w^USp                     ;S* 

'•'     .',■:'                        •■"..■ 

Fig.   43. — Top-grafting;  large  black  walnut  tree  top-worked.     Mr.  J.  F.  Bur- 
gess, Superintendent  Vrooman  ranch. 


244 


UNIVERSITY    OF    CALIFORNIA  —  EXPERIMENT    STATION. 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  245 

DIGGING. 

For  removing  walnut  trees  from  the  nursery  no  better  method  has 
been  devised  than  simply  digging  out  each  tree  individually  by  hand 
with  long-handled  shovels.  Plowing  the  dirt  away  is  of  very  little 
assistance  and  puts  the  ground  into  bad  shape  for  walking  and  standing 
upon  during  digging,  especially  in  muddy  weather.  Usually  the  best 
that  can  be  done,  especially  with  good  sized  trees,  is  to  simply  dig  out 
each  tree  entirely  by  hand.  In  doing  this  opinions  differ  as  to  the 
amount  of  the  taproot  which  should  be  preserved,  and  often  the  desires 
of  the  purchaser  must  be  followed  to  some  extent  in  this  matter,  whether 
or  not  they  agree  with  the  ideas  of  the  nurseryman.  One  of  the  most 
popular  fallacies  is  that  concerning  the  taproot  of  the  walnut  tree, 
many  people  holding  strongly  to  the  view  that  the  root  must  be  kept 
intact,  even  to  a  length  of  three  or  four  feet,  in  order  to  insure  proper 
growth  of  the  tree  after  planting  in  the  orchard.  This  idea  has  been 
abundantly  disproven,  and  the  fact  is  well  established  that  a  root  not 
more  than  eighteen  or  twenty  inches  in  length,  if  well  branched,  and 
especially  if  the  top  is  properly  cut  back,  usually  makes  a  better  tree 
than  one  much  longer.  Walnut  taproots  are  very  large  in  diameter  in 
proportion  to  the  size  of  the  top  and  are  composed  of  very  soft,  spongy 
bark  and  wood.  This  tissue,  if  conditions  are  not  such  as  to  start  the 
root  into  growth  promptly,  is  very  susceptible  to  decay,  and  a  long,  un- 
branched  taproot  is  much  more  likely  to  remain  in  the  ground  without 
sending  out  new  growth  until  it  begins  to  decay  than  a  shorter,  well 
branched  root.  Fig.  45  represents  the  most  desirable  types  of  Avalnut 
roots,  2  being  of  a  more  branching  type  than  1.  Roots  like  these  send 
out  new  growth  quickly  and  are  in  all  respects  the  most  desirable  form. 
In  digging,  therefore,  care  should  be  exercised  not  to  cut  off  or  bruise 
the  lateral  roots  within  about  a  foot  of  the  main  stalk  and  the  taproot 
may  then  be  cut  off  at  a  depth  no  greater  at  most  than  two  feet.  Even 
this  is  more  than  is  necessary  if  the  root  is  well  branched.  Some  roots 
will  be  found  which  do  not  have  any  taproot  even  of  this  length,  and  in 
such  cases  the  main  laterals  should  be  preserved  in  good  condition.  It  is 
well  to  dig  the  trees  as  early  as  possible  in  the  winter  in  order  to  have 
them  ready  for  sale  to  the  first  customers  and  to  avoid  the  danger  of 
being  caught  by  long-continued  rainy  weather  during  which  the  trees 
can  not  be  dug.  Digging  may  commence  as  soon  as  the  leaves  have 
fallen,  although  unless  fairly  heavy  rains  have  fallen  it  may  be  found 
necessary  to  irrigate  the  ground  in  order  to  facilitate  the  work.  After 
the  trees  are  dug,  if  they  are  not  wanted  for  immediate  delivery  they 
may  be  heeled  in  at  some  convenient  place  by  digging  a  trench  in  which 
the  roots  are  placed  and  thoroughly  covered  with  earth.  It  is  sometimes 
convenient  to  put  each  tree  back  in  the  same  hole  from  which  it  was  dug, 


246 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


covering  the  root  again  with  loose  earth,  when  it  can  easily  be  pulled 
out  by  hand  when  wanted.  Before  delivery  or  planting  the  trees  should 
be  carefully  gone  over  with  shears  and  pruning  saw,  cutting  off  all 
broken  roots  and  ragged  ends  back  to  good  tissue,  trimming  off  all 


Fig.   45. — 1,    a  good  graft  union  and  root ;  2,  a  good  graft  union  and  ideal  branching 
root.     A,  original  seedling  nut ;  B,  graft  union  ;  C,  upper  end  of  original  scion. 

remains  of  sprouts  or  stubs  of  any  sort  and  cleaning  them  up  into  a  good 
sound  root  and  a  clean  stem.  All  cuts  on  the  crown  or  stem  should  be 
covered  with  grafting  wax.  Fig.  46 — 1  shows  a  grafted  tree  which  has 
made  a  very  poor  union,  leaving  a  large,  dead,  decaying  stub  where  the 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  247 

original  seedling  top  was  cut  off.     It  is  not  necessary  that  every  tree 
should  have  this  stub  completely  grown  over  in  the  nursery  in  order  to 


Fig.  46. — 1,  a  poor  graft  union;  2,  a  good  graft  union  on  a  root    which  has  been 
grafted  unsuccessfully  once  or  twice  before. 

make  it  worthy  of  planting,  but  those  with  very  poor  union  such  as  this 
are  of  doubtful  value  and  should  be  discarded  if  first-class  trees  are 


248  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

desired.  Fig.  46 — 2  shows  a  one-year-old  graft  on  a  root  which  was  two 
years  old  at  the  time  of  grafting,  a  graft  having  failed  the  previous  year. 
In  this  case  the  crown  of  the  root  is  still  sound,  showing  scars  of  suckers 
which  have  completely  healed  over  except  when  recently  cut.  This  tree 
is  unobjectionable,  but  such  are  sometimes  seen  with  very  large,  old 
clumsy  roots  with  a  poorly  healed  union  and  scars  at  the  crown.  These 
are  not  to  be  desired.  Fig.  45  shows  perfect  trees,  although  the  rough 
ends  where  the  roots  were  cut  off  have  not  yet  been  trimmed.  In 
Fig.  45 — 2  the  original  nut  from  which  the  seedling  grew  may  be  seen 
at  A,  the  point  of  grafting  at  B  and  the  upper  end  of  the  scion  at  C. 

After  cleaning  up  the  roots  and  lower  part  of  the  stem  the  next  ques- 
tion is  that  as  to  cutting  back  the  top.  Here,  again,  radical  differences 
of  opinion  exist,  some  growers  holding  a  strong  preference  for  plant- 
ing the  largest  sized  trees  without  cutting  back  the  top  at  all,  some 
preferring  a  small  tree  likewise  without  cutting,  while  others  would 
cut  the  top  back  at  various  heights.  Assuming  that  the  root  and  top 
are  of  the  same  proportionate  size,  the  same  rules  as  to  cutting  back 
must  apply  either  with  large  or  small  trees.  v  There  is  considerable 
unanimity  on  one  point,  namely,  that  the  walnut  tree  in  orchard  form 
should  be  headed  considerably  high,  at  a  point  about  five  or  six  feet 
from  the  ground.  It  is,  therefore,  possible  to  obtain  this  with  trees  of 
about  this  height  when  planted  by  not  cutting  them  at  all,  with  trees 
of  greater  height  than  this  by  cutting  them  back  to  such  a  height,  or 
with  smaller  trees  by  planting  them  either  as  they  are  or  after  cutting 
back  and  allowing  one  shoot  to  grow  up  into  a  trunk,  heading  this  at 
the  desired  height.  Even  when  very  tall  trees  are  planted  without  cut- 
ting they  usually  branch  naturally  at  somewhere  about  this  height,  and 
if  the  tops  do  not  die  back  the  ultimate  form  of  the  tree  is  very  much 
the  same  with  a  tall  tree  whether  it  is  cut  or  not.  The  chief  objection 
to  planting  out  trees  with  uncut  tops  is  that  the  roots  have  necessarily 
been  cut  off  more  or  less  and  are,  therefore,  not  able  to  send  up  as  much 
moisture  to  the  top  as  is  required.  Such  being  the  case,  there  is  dan- 
ger of  the  top  dying  back  before  a  proper  connection  with  the  soil  is 
reestablished  by  the  root,  or  if  it  does  not  die  back  it  may  remain  nearly 
dormant  for  some  time,  making  very  little  growth  and  becoming  very 
liable  to  sunburn.  In  such  cases  the  tree  may  stand  for  one  or  several 
years  before  starting  vigorous  growth  in  the  top  and  during  this  time 
the  trunk  may  become  so  badly  sunburned  that  it  is  seriously  crippled 
for  life.  The  liability  of  such  an  occurrence  depends  largely  upon  the 
size  of  the  root,  amount  of  moisture  in  the  soil  and  the  degree  to  which 
the  root  dried  out  during  the  time  after  it  was  dug  from  the  nursery 
and  before  it  was  planted  in  the  orchard.  Trees  which  are  moved  only 
a  short  distance,  especially  if  the  root  is  dug  with  extra  care,  may  start 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA. 


249 


Fig.  4  7. — A  tree  planted  when  about  four  feet  high  without  cutting  back.  The  space 
between  the  hands  indicates  the  following  year's  growth  of  the  leader,  and  that 
above  the  left-hand  the  growth  of  the  second  year. 


250 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


into  good  growth  the  first  season  and  flourish  satisfactorily  even  with- 
out any  cutting  back  of  the  top.  More  often,  however,  the  root  becomes 
more  or  less  dried  in  handling  and  shipping,  the  ground  in  the  orchard 


Fig.   4  8.— Three-year-old  tree,  which  was  cut  back  to  five  and  one  half  feet  before 

planting. 

may  lack  moisture  to  some  extent  during  the  first  season  and  altogether 
the  chances  are  strong  that  the  tree  planted  without  cutting  back  will 
not  get  a  very  good  start  the  first  year  and  may  receive  a  serious 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  251 

setback.  In  planting  an  orchard  to  be  grown  without  irrigation  the 
chances  of  this  are  very  much  greater  and  the  objections  to  planting 
without  cutting  back  are  increased  many  fold.  If  the  tops  are  to  be 
cut  at  all,  one  thing  is  clear ;  namely,  that  they  should  either  be  cut  at 
the  point  where  the  head  is  to  be  established;  namely,  at  a  height  of 
five  or  six  feet,  or  if  cut  lower  one  sprout  must  be  brought  up  and 
formed  into  a  new  trunk.  Trees  cut  off  five  or  six  feet  from  the  ground 
are  more  likely  to  start  well  than  those  not  cut  at  all,  but  even  at  this 
height  a  long  stretch  of  the  old  wood  remains,  which  under  slightly 
unfavorable  conditions  may  become  sunburned,  dried  out,  or  semi-dor- 
mant. After  this  has  once  happened  during  the  time  while  the  root  is 
establishing  a  new  connection  with  the  soil,  the  flow  of  the  sap  becomes 
sluggish  and  impeded  and  the  tree  cannot  develop  with  full  vigor  until 
new  wood  is  formed. 

Observation  and  experience  have  led  us  strongly  to  the  belief  that 
in  the  long  run  and  in  the  majority  of  instances  better  and  more  vigor- 
ous trees  will  be  obtained  by  cutting  back  the  top  fairly  close  to  the 
ground  and  bringing  up  one  strong,  new  shoot  to  form  a  new  trunk  and 
top  of  the  tree,  rather  than  by  attempting  to  preserve  any  considerable 
portion  of  the  original  stem.  If  such  cutting  is  to  be  done  there  is  no 
apparent  advantage  in  leaving  more  than  two  feet  of  the  original  trunk 
at  the  most,  since  the  whole  idea  is  based  on  the  belief  that  it  is  better 
to  grow  a  new  trunk  than  to  keep  the  old  one.  If  such  is  the  object 
desired,  there  is  manifestly  no  advantage  in  cutting  off  at  four  or  three 
feet,  since  in  such  a  case  we  still  have  remaining  a  considerable  length 
of  wood  subject  to  the  objections  mentioned,  and  at  the  same  time  a 
length  which  would  be  attained  within  a  few  days  by  a  vigorous  new 
shoot.  It  is,  therefore,  our  belief  that  the  best  results  will  be  obtained 
by  cutting  the  tops  back  so  that  there  remain  simply  enough  buds  to 
insure  one  good  sprout  to  form  a  new  stem.  This  can  be  obtained  by 
leaving  not  over  eighteen  inches  or  even  twelve  inches  in  most  cases. 
It  will  sound  to  many  extremely  radical  and  unnecessary  with  nursery 
trees,  some  of  which  may  be  twelve  or  fifteen  feet  in  height  and  two 
inches  in  diameter  at  the  base,  to  cut  off  these  fine  tops  ruthlessly  to 
a  length  of  only  twelve  or  eighteen  inches.  Yet,  such  a  tree  with  a 
twelve-inch  top  and  a  strong,  well-branched  eighteen-  to  twenty-four- 
inch  root  will  send  up  a  shoot  which  in  almost  every  instance  will  pro- 
duce a  top  superior  to  that  of  trees  which  were  left  uncut  or  cut  back 
to  a  height,  say,  of  five  or  six  feet.  Furthermore,  the  new  trunk  will 
be  composed  of  absolutely  fresh,  vigorous  tissue,  highly  resistant  to 
sunburn,  free  from  die-back,  and  of  the  most  desirable  type  in  every 
way.  It  is,  therefore,  our  well-considered  recommendation  that  in  pre- 
paring walnut  trees  for  planting  the  tops  should  be  cut  off  to  a  length 


252  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


Fig.  49. — Tree  cut  back  to  two  feet  before  planting.     The  whole  top  above  the  finger 
is  composed  of  new  growth. 


Bulletin   2  31]  WALNUT    CULTURE    IN    CALIFORNIA.  253 

of  not  over  eighteen  inches,  after  which  the  cut  ends  should  be  carefully 
sealed  over  with  grafting  wax.  We  would  do  this  with  trees  of  all 
sizes,  and  would  insist  particularly  upon  such  a  practice  with  trees 
going  into  non-irrigated  orchards.  After  trimming,  cutting  and  wax- 
ing, the  roots  should  still  be  kept  moist,  either  by  heeling  them  in, 
planting  at  once  in  the  orchard  or  proper  packing,  if  they  are  to  be 
shipped. 

PLANTING. 

In  planting  the  walnut  orchard  the  ground  should  be  thoroughly  pre- 
pared as  for  other  fruit  trees  and  staked  off  for  the  trees  at  the  desired 
distance  apart,  which  subject  we  have  discussed  elsewhere.  A  large 
hole  should  be  dug  for  each  tree,  considerably  larger  than  the  root,  and 
with  the  heavy  subsoil  best  suited  to  the  walnut  it  is  extremely  advisable 
that  a  stick  of  dynamite  be  discharged  at  a  still  greater  depth  below  the 
hole.  This  should  then  be  filled  in  with  top  soil,  up  to  proper  depth 
for  the  tree.  The  tree  is  then  put  in  place,  planting  it  fully  as  deep  or 
a  little  deeper  than  it  stood  in  the  nursery  and  the  soil  should  be  thor- 
oughly tramped  and  settled  about  the  roots.  If  not  well  planted,  a  thick 
soft  root  like  that  of  the  walnut  is  liable  to  decay,  and  special  pains 
should  therefore  be  taken  to  settle  the  soil  firmly  about  the  roots  so  that 
they  will  immediately  begin  to  absorb  moisture  and  commence  new 
growth.  Planting  may  be  done  at  any  time  after  the  trees  are  ready, 
usually  the  earlier  in  the  winter  the  better,  in  order  to  take  advantage  of 
the  settling  and  moistening  of  the  ground  by  the  winter  rains.  After 
planting,  the  trees  should  be  carefully  watched  to  see  that  they  are  all 
doing  as  well  as  possible  and  not  suffering  in  any  avoidable  way.  If  a 
considerable  portion  of  the  top  has  been  left  without  cutting  back,  this 
should  be  protected  from  sunburn  by  tying  about  it  a  rather  loose  wrap- 
ping of  cornstalks,  tules,  or  special  protectors  made  for  this  purpose. 
It  is  not  well  to  wrap  the  trunks  tightly  in  paper  or  cloth,  as  this  makes 
the  bark  more  tender  after  the  wrapping  is  removed.  If  the  tops  have 
been  cut  black  close  to  the  ground  one  good  sprout  should  be  selected  to 
form  the  new  stem,  and  as  soon  as  the  growth  of  this  is  assured  all  the 
others  which  start  should  be  cut  off.  Usually  the  most  vigorous  sprout 
should  be  chosen,  but,  other  things  being  approximately  equal,  it  is 
better  to  take  the  one  closest  to  the  ground  and  one  on  the  windward 
side  of  the  trunk.  A  good  sized,  at  least  a  2  by  2  stake  should  be  set  in 
the  ground  close  to  the  tree,  to  which  the  shoot  may  be  tied  up.  The 
shoot  should  then  be  tied  once  or  twice  to  this  stake  in  a  similar  manner 
as  is  done  in  the  nursery  until  it  reaches  a  height  of  about  six  feet,  when 
it  should  be  topped  and  caused  to  branch.  After  this  shoot  is  well  estab- 
lished the  remaining  stub  of  the  old  stem  should  be  cut  off  closely  above 
it  and  the  scar  waxed  over. 


254  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

VARIETIES  OF  THE  ENGLISH  WALNUT. 

The  fact  has  been  frequently  alluded  to  in  this  bulletin  that  great 
variation  exists  in  various  individual  seedling  trees  of  the  English 
walnut,  and  that  as  a  result  of  such  variation  a  fairly  large  number  of 
distinct  varieties  has  been  established,  each  of  these  having  originated 
from  a  particular  tree  which  was  selected  by  some  one  as  being  particu- 
larly desirable  on  account  of  certain  qualities.  Some  of  these  varieties, 
notably  certain  French  varieties  close  to  two  hundred  years  old,  have 
been  kept  pure  since  the  original  tree  was  first  selected,  by  budding  or 
grafting.  Others,  especially  the  majority  of  the  varieties  now  most  com- 
mon in  California,  are  of  comparatively  recent  origin  and  represent  the 
grafted  or  budded  offspring  of  certain  seedling  trees  in  the  State  which 
have  seemed  especially  desirable  and  have  therefore  been  propagated 
from  and  in  some  cases  widely  advertised  and  sold  on  quite  an  extensive 
scale.  The  variations  which  occur  in  seedling  walnuts  consist  in  a 
marked  difference  in  the  vigor  and  size  of  the  tree,  its  rapidity  of 
growth,  its  general  form  or  aspect,  and  that  of  its  foliage,  the  color  and 
texture  of  the  bark,  the  time  of  budding  out  in  the  spring,  the  amount  of 
catkins  and  pollen  produced,  its  productiveness,  season  of  maturity  of 
the  crop,  and  the  size,  form,  color,  flavor,  and  other  characteristics  of  the 
nut.  Also  the  susceptibility  of  the  tree  to  various  diseases  and  inju- 
rious influences.  Seedling  walnuts  vary  very  greatly  in  these  respects, 
although  certain  general  types  of  a  certain  degree  of  similarity  among 
themselves  may  be  recognized.  Thus,  in  California,  almost  all  the 
so-called  Santa  Barbara  seedlings  come  out  comparatively  early  in  the 
spring,  they  are  usually  thrifty,  large  trees  under  favorable  conditions, 
and  the  nuts  are  mostly  of  the  soft-shell  type  as  regards  cracking  qual- 
ity. The  old  fashioned  hard  shells  represent  another  fairly  uniform 
type,  even  when  grown  from  seed,  having  rather  small,  round,  very 
hard-shelled  nuts  borne  upon  trees  with  a  certain  similarity  to  one 
another.  The  same  is  true  of  the  so-called  paper  shells.  Trees  of  all 
these  types  bear  nuts  of  about  the  same  color,  a  dull,  neutral  or  greyish 
brown.  Taking  the  French  varieties  we  find  among  most  of  them  the 
habit  of  coming  out  extremely  late  in  the  spring,  so  that  a  Franquette, 
Mayette,  or  Parisienne,  and  almost  all  the  seedlings  derived  from  nuts 
of  these  varieties,  leaf  out  several  months  later  than  Chase,  Placentia 
Perfection,  or  most  of  the  Santa  Barbara  Soft  Shell  seedlings,  even 
though  planted  in  the  same  locality.  They  also  bear  nuts  almost  always 
of  a  brighter,  more  yellowish  color  than  do  the  California  varieties.  The 
meat  of  the  nut  is  also  usually  lighter  colored. 

In  other  words,  we  find  in  walnuts  certain  types  differing  very 
widely  in  various  respects  from  one  another,  while  among  the  seedlings 
from  one  of  these  types  there  is  a  considerable  variation,  but  not  so  great 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  255 

as  that  between  the  different  types  themselves.  The  various  types,  indi- 
vidual trees  and  varieties  now  to  be  found  in  California  have  almost  all 
descended,  as  we  have  shown  on  page  171,  from  two  sources,  namely,  the 
Santa  Barbara  Soft  Shell  type,  first  produced  and  propagated  by 
Joseph  Sexton  of  Goleta,  which  came  probably  from  Chile,  and  second, 
various  French  varieties  and  their  derivatives,  almost  all  of  which  were 
first  introduced  or  developed  by  Felix  Gillet.  It  is  doubtless  true  that 
more  than  99  per  cent  of  the  walnut  trees  now  growing  in  this  State  are 
descendants  of  one  or  the  other  of  these  sources.  The  only  noticeable 
exception  to  this  is  the  Eureka,  which  originated  as  a  chance  seedling 
from  a  tree  introduced  through  another  source.  It  is  undoubtedly  true 
that  with  the  exception  of  the  Eureka  all  the  varieties  which  are  worthy 
of  discussion  for  California  planting  are  either  Santa  Barbara  Soft 
Shell  seedlings,  old  French  varieties,  or  seedlings  of  some  of  these  later 
varieties  which  have  originated  in  California. 

In  discussing  the  various  varieties  now  before  the  public  we  should 
first  of  all  formulate  an  idea  or  standard  as  to  what  constitutes  an  ideal 
walnut.  In  regard  to  this,  the  first  and  most  important  quality  is  un- 
doubtedly that  of  production.  A  variety  however  fancy  or  otherwise 
desirable  which  does  not  produce  comparatively  large  crops  of  nuts  can 
not  be  considered  satisfactory,  whatever  may  be  its  other  qualities.  As 
to  the  ideal  or  greatest  possible  production,  we  may  say  that  while  the 
crop  of  the  present  producing  seedling  groves  of  southern  California 
averages  only  about  50  pounds  per  tree,  or  1,000  pounds  per  acre,  there 
are  numerous  individual  seedling  trees  in  the  State  which  average  close 
to  300  pounds,  and  a  very  large  number  which  produce  regularly  more 
than  200  pounds.  Since  thrifty  walnut  trees,  after  reaching  an  age  of 
twelve  to  fifteen  years,  should  have  a  distance  of  at  least  fifty  to  sixty 
feet  apart,  which  means  an  average  of  not  over  fifteen  trees  per  acre, 
we  may  estimate  that  at  200  pounds  per  tree  the  crop  per  acre  would 
equal  3,000  pounds  of  nuts,  which  at  an  average  price  of  12  cents  would 
amount  to  $360  gross  per  acre.  This  figure,  as  compared  with  present 
returns  from  the  citrus  industry,  is  fairly  modest,  yet  if  it  could  be 
maintained  as  a  regular  income  it  would  represent  a  very  satisfactory 
return  on  much  of  the  land  in  this  State  which  is  adaptable  to  walnut 
culture.  On  the  highest  priced  citrus  lands  of  the  south,  walnuts  even 
on  this  basis  could  hardly  compete  with  lemons  and  oranges.  Three- 
hundred-pound  trees  would  add  50  per  cent  to  the  figure  estimated  and 
such  production  should  be  ultimately  attained  in  an  ideal  tree  having 
plenty  of  room  at  least  by  the  time  it  reaches  fifteen  or  twenty  years 
of  age.  As  we  have  said  above,  however,  these  results  are  far  above  those 
actually  being  obtained  at  present  in  the  walnut  industry.  At  this 
point  we  may  also  consider  the  relative  merits  of  a  fancy  variety,  pro- 


256  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

ducing  nuts  which  may  sell  for  at  least  25  cents  per  pound,  but  pro- 
ducing only  50  to  100  pounds  on  mature  trees,  as  against  a  12  or  15 
cent  variety  which  produces  200  or  300  pounds.  The  comparative  desir- 
ability of  such  varieties  for  planting,  so  far  as  they  actually  exist,  can 
be  judged  fairly  well  from  our  description  of  the  various  kinds.  The 
relation  between  quality  of  nut  and  the  amount  of  the  product  should 
be  very  carefully  considered  in  choosing  a  variety  for  planting  and  the 
grower  should  not  be  too  much  influenced  by  the  appearance  of  a  few 
sample  nuts  without  regard  to  the  quantity  in  which  they  are  produced. 
The  ideal  tree,  of  course,  is  one  which  would  produce  large  crops  of  the 
most  desirable  type  of  nuts,  but  this  combination  has  not  been  fully 
attained.  Another  important  point  in  regard  to  production  is  that  of 
the  precocity  or  age  of  coming  into  bearing,  in  which  great  differences 
exist  in  different  varieties  and  between  individual  seedling  trees.  Some 
varieties  begin  to  produce  nuts  quite  abundantly,  even  in  the  nursery, 
and  give  a  commercial  crop  within  three  years  from  planting  in  the 
orchard,  while  others  are  several  years  later  in  coming  into  bearing. 
Here,  again,  this  quality  must  be  carefully  weighed  in  choosing  a  variety, 
considering  its  relative  value  in  proportion  to  other  qualities.  There  is 
in  this  connection  the  possibility  of  inter-planting,  either  with  more  pre- 
cocious walnuts  or  some  other  crop,  which  may  offset  the  disadvantage 
of  an  otherwise  desirable  variety  which  is  slow  in  coming  into  bearing. 
The  next  important  consideration  is  that  of  the  size  and  weight  of 
the  nuts.  In  almost  all  varieties  and  seedling  trees  the  nuts  are  of  good 
size  when  the  trees  are  young  and  first  come  into  bearing,  but  in  many 
there  is  a  tendency  for  the  nuts  to  become  smaller  and  smaller  as  the 
trees  get  older  and  the  crops  heavier.  The  size  of  commercially  first 
grade  California  walnuts,  as  we  have  shown  on  page  197,  is  repre- 
sented by  nuts  which  will  not  pass  through  a  one  inch  square  opening, 
while  those  above  1  3-16  inches  command  a  considerable  premium. 
Nuts  of  a  size  considerably  greater  than  this  are  in  demand  at  still 
higher  prices  to  some  extent,  but  ordinarily  the  market  for  such  large 
nuts  is  quite  limited,  owing  to  the  fact  that  most  varieties  of  this  sort 
are  poorly  filled  with  meat.  Whether  an  extra  large,  well  filled  nut 
and  one  of  good  flavor,  if  such  exists  or  could  be  produced,  would  be 
desirable  for  general  planting,  is  somewhat  problematical,  although 
certainly  such  a  nut  would  command  a  ready  sale  and  at  a  good  price 
to  a  considerable  extent.  However  this  may  be,  it  is  true  that  on  the 
basis  of  present  standards  the  most  desirable  size  is  that  which  is  not 
graded  out  by  a  square-mesh  screen  of  1  3-16  inches,  but  not  so  very 
much  larger  than  this.  The  weight  of  the  nut  is  equally  important, 
since  this  varies  widely  in  nuts  of  the  same  size,  as  may  be  seen  in  the 
table  on  page  300.     It  may  be  seen  here  that  some  of  the  largest 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  257 

varieties  are  considerably  lighter  in  weight  than  others  in  which  the 
nuts  are  decidedly  smaller.  A  desirable  nut  should  be  well  filled  with 
plump  meat  without  too  much  air  space  between  the  shell  and  the  meat. 
A  comparatively  heavy  shell  is  more  desirable  than  a  very  thin,  light 
one,  since  the  nut  is  better  protected,  less  susceptible  to  perforation  and 
similar  troubles  (see  page  376),  and  it  is  also  to  be  considered  that 
since  walnuts  are  sold  by  the  pound,  the  heavier  the  shell  the  greater 
is  the  weight  and  the  more  the  returns  from  a  given  number  of  nuts. 
Next  to  be  considered  is  the  shape,  smoothness,  uniformity  and  color  of 
the  nuts.  These  qualities  may  be  sometimes  of  minor  importance  where 
walnuts  are  grown  on  a  very  large  scale  and  put  upon  the  market  without 
individuality  of  any  kind,  yet  for  an  ideal  nut  or  for  one  which  is  to 
command  the  highest  price,  certain  qualifications  are  very  desirable 
in  these  respects.  The  most  attractive  form  is  usually  considered  to 
be  a  somewhat  elongated  walnut,  rather  broader  at  the  base  than  at 
the  apex.  This  is  not  very  important,  however,  since  the  smoothness, 
symmetry,  and  uniformity  of  the  nuts  affect  their  attractive  appear- 
ance more  than  their  shape.  An  ideal  nut  should  be  quite  smooth,  free 
from  decided  ridges,  grooves,  or  other  irregularities  of  surface ;  it  should 
be  symmetrical  rather  than  one-sided  or  irregularly  shaped,  and  all 
the  nuts  should  be  of  the  same  general  shape  and  appearance,  giving 
them  uniformity  and  individuality.  A  variety  in  which  the  nuts  are 
decidedly  uniform  so  that  the  variety  is  easily  distinguished  and  recog- 
nized, even  by  the  ordinary  purchaser,  has  a  marked  advantage  over 
one  in  which  the  nuts  are  of  all  sorts  of  shapes  so  that  only  an  expert 
can  distinguish  the  variety  from  others.  The  color  of  the  nut  is  also  of 
considerable  importance,  although  walnuts  are  almost  always  bleached 
before  putting  them  on  the  market- and  in  this  way  they  are  all  brought 
to  about  the  same  color.  A  variety,  however,  which  is  of  a  light,  attrac- 
tive color,  is  entitled  to  considerable  merit  over  one  which  is  dull,  dark 
or  unattractive. 

Next  we  may  consider  the  cracking  quality  and  sealing  of  the  nut. 
A  thin-shelled-  easily-opened  nut  is  somewhat  more  attractive  to  the 
eater  than  one  which  is  hard  and  difficult  to  open,  yet  from  a  com- 
mercial standpoint  this  quality  is  a  comparatively  unimportant  one. 
A  rather  firm-shelled  nut,  and  especially  one  which  is  strongly  sealed 
at  the  natural  line  of  opening  or  suture  between  the  two  halves  of  the 
shell,  is  very  much  to  be  preferred  to  one  which  pops  open  at  the 
slightest  pressure.  In  the  latter  case  many  of  the  nuts  open  in  drying, 
or  when  shaken  about  in  the  sacks  and  bins,  moisture  and  mold  spores 
are  admitted,  many  are  spoiled  in  handling,  and  such  a  nut  is  in  every 
way  very  undesirable  to  the  grower  and  of  only  very  slight  advantage 
to  the  consumer.     Concerning  walnuts  for  the  table,  they  are  almost 

10—231 


258  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

always  cracked  beforehand  in  any  case,  and  the  necessity  of  a  little 
pressure  more  or  less  is  of  very  slight  importance.  No  variety  can  be 
harvested,  handled,  marketed  and  kept  for  any  length  of  time  with 
good,  plump,  white  meats,  free  from  mold  and  discoloration  unless  the 
shell  is  fairly  hard  and  thoroughly  well  sealed.  Extreme  thinness  of 
shell  is  one  of  the  least  important  qualifications  and  is  in  fact  decidedly 
undesirable.  The  color  of  the  meat  is  of  considerable  importance.  As 
commercially  graded  in  California,  nuts  with  the  lightest  colored  meats 
are  considered  most  desirable,  while  those  which  are  decidedly  dark, 
even  though  plump  and  of  good  flavor,  are  discriminated  against.  It 
is,  therefore,  true  that  the  lighter  colored  the  meat  the  more  desirable 
is  the  nut,  and  a  variety  in  which  the  nuts  run  uniformly  quite  dark- 
meated  is  decidedly  objectionable.  The  flavor  of  the  meat  varies  con- 
siderably in  different  varieties  and  is  of  much  importance  in  a  high 
class,  fancy  trade.  In  some  varieties  the  nut  is  sweet  and  of  a  pleasant 
flavor,  while  the  most  common  undesirable  quality  in  this  respect  is  a 
bitter  flavor.  This  should  be  guarded  against  in  choosing  an  ideal 
variety. 

To  sum  up,  then,  the  most  important  qualifications  in  a  walnut 
variety  from  a  strictly  commercial  standpoint  are  that  it  should  be  a 
uniformly  large  producer  of  nuts  the  majority  of  which  will  not  pass 
through  a  1  3-16  square  mesh,  and  of  which  very  few  pass  through  a 
smaller  opening  than  a  1  inch  size.  These  nuts  should  be  well  sealed, 
even  though  somewhat  hard  shelled,  and  should  be  uniformly  well  filled 
with  meat  of  light  yellowish  brown  color  or  not  darker  than  light  brown 
or  amber.  For  a  more  fancy  trade  the  nuts  should  be  of  attractive, 
uniform  shape  and  color,  smooth  surface,  and  particularly  high  quality 
and  agreeably  flavored  meat.  A  variety  which  would  combine  all  these 
characteristics  to  a  very  high  degree,  including  both  those  of  production 
and  quality,  would  form  the  basis  of  a  crop  which  even  the  citrus  in- 
dustry could  scarcely  equal  in  attractiveness  and  profit. 

COMMERCIAL  VARIETIES. 

The  following  seven  varieties  will  be  most  fully  described,  being  those 
of  which  nursery  trees  are  most  commonly  available  and  those  which 
we  have  been  able  to  see  growing  and  obtain  nuts  from  for  a  period  of 
several  years.  Some  of  the  varieties  in  our  second,  miscellaneous  list- 
may  be  better  than  any  of  these,  but,  if  so,  their  merits  have  not  yet 
been  fully  established. 

CHASE. 

Origin. 

This  variety  originated  in  a  tree  standing  about  three  miles  south 
of  Whittier  upon  a  ranch  formerly  called  the  Chase  place,  which  has 
changed  hands  several  times  during  the  last  few  years.    The  tree  is  said 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  259 

to  have  been  planted  in  1886  among  a  lot  of  seedlings  obtained  from 
Felix  Gillet.  One  story  has  it  that  the  tree  is  a  seedling  of  the  Mesange 
variety,  although  we  are  unable  to  trace  the  origin  of  this  idea.  The 
nut  certainly  has  no  resemblance  to  that  of  the  variety  mentioned  but 
seems  to  be  of  the  Santa  Barbara  Soft  Shell  type.  The  variety  owes 
its  prominence  to  Mr.  A.  R.  Rideout,  of  Whittier,  who  has  propagated, 
sold  and  advertised  it  widely  during  the  past  few  years.  It  has  not  yet 
been  tested  to  any  extent  in  the  north,  although  quite  extensive  plants 
ing  of  the  variety  has  recently  been  made  in  that  part  of  the  State. 

NUT. 
Size. 

Medium  to  large  on  young  trees,  small  on  original  tree.  On  young 
trees  average  1£  by  If  by  If  inches,  with  many  larger.  Nuts  on  old 
tree  much  smaller,  with  many  less  than  1  inch  long. 

Form. 

Broadly  oval  or  rounded,  symmetrical,  flattened,  apex  and  base  of 
equal  breadth.  Apex  terminating  in  a  short  and  pronounced  point  or 
beak. 

Surface. 

Quite  smooth  and  even. 

Color. 

Neutral  light  brown,  without  the  pinkish  cast  of  Placentia  Perfection. 

Uniformity. 

Strong,  in  trees  of  real  Chase  origin.  In  some  cases  the  variety  has 
become  mixed  with  other  kinds,  which  probably  accounts  for  some 
apparent  deviations  from  the  type. 

Cracking   Quality. 

Nuts  poorly  sealed,  both  at  apex  and  base,  so  that  they  are  very  easily 
opened  with  the  fingers. 

Pellicle. 

Light  tan  to  light  brown. 

Meat. 

Uniformly  plump  and  well  filled.  Averaging  nearly  50  per  cent  of 
total  weight  of  meat,  at  the  same  time  having  a  heavy  shell. 

Flavor. 

Not  pronounced.    Mild  and  free  from  any  decided  characteristic. 

TREE. 
Foliation  Period. 

Very  early.  About  the  earliest  of  any  named  variety.  Earlier  in 
southern  California  than  the  average  of  the  seedlings. 


260  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

Growth. 

Very  vigorous  and  thrifty.  Young  trees  have  a  characteristic,  up- 
right, rather  stiff  appearance,  the  branches  being  straight  and  all 
coming  from  the  uprights  at  the  same  angle.  This  appearance  is  lost 
after  fruit  spurs  become  abundant. 

Foliage. 

Abundant  and  thrifty. 

Harvest  Season. 

Early. 

Precocity. 

Quite  strong  in  the  south.    One  of  the  best  in  this  respect. 

Production  in  Older  Trees. 

The  original  tree  is  said  to  have  produced  325  pounds  in  one  year 
and  is  uniformly  a  large  producer.  This  is  due  to  its  great  size  as  well 
as  fruitfulness,  as  there  are  few  larger  walnut  trees  in  the  State  than 
this.  Our  own  five  years'  observation  of  this  tree  has  shown  it  to  be 
unusually  thrifty  and  vigorous  and  a  bearer  of  heavy  crops,  even  under 
adverse  conditions.  Its  long  sustained  vigor  of  growth  is  in  fact  the 
most  valuable  characteristic  of  the  variety. 

Susceptibility  to  Blight  and  Other  Troubles. 

The  original  tree  shows  considerably  less  blight  than  its  neighbors, 
although  not  immune  tr  the  disease.  It  is  so  large,  vigorous  and  thrifty 
that  good  crops  are  produced  in  spite  of  the  disease.  The  same  vigor 
of  growth,  together  with  the  abundance  of  foliage  protects  the  nuts  to 
a  large  extent  from  sunburn  and  other  climatic  injuries.  The  nuts  of 
the  original  tree  have  been  decidedly  free  from  sunburn  as  compared 
with  those  of  neighboring  trees. 

Some  young  groves  of  this  variety  have  shown  considerable  perfora- 
tion in  the  nuts,  but  the  old  tree  is  noticeably  free  from  this  trouble. 
See  page  376. 

GENERAL   REMARKS. 

From  the  above  description  we  may  sum  up  the  characteristics  of  the 
Chase  variety  by  saying  that  it  is  a  very  large,  thrifty,  vigorous-growing 
tree,  which  on  account  of  its  vigor  of  growth  is  a  good  producer  and 
comparatively  free  from  disastrous  losses  by  blight  or  other  injurious 
influences.  Its  nuts  have  no  exceptional  characteristics,  but  are  of  good 
average  quality  as  compared  with  the  product  of  the  present  groves  of 
southern  California.  The  tree  has  considerable  precocity  in  bearing  and 
may  therefore  be  recommended  to  those  who  desire  quick  results,  both  in 
growth  of  tree  and  production  of  nuts. 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA. 


261 


Fig.   50. — Chase  walnut,  natural  size. 


262  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


Fig.   51. — Chase  walnut,  natural  size. 


Bulletin  231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


263 


CONCORD. 

Origin. 

This  variety  originated  in  a  seedling  tree  on  the  place  of  Mr.  George 
M.  Westcott,  of  Concord,  Contra  Costa  County.  The  original  tree  came 
from  the  late  Felix  Gillet  and  is  said  to  have  been  a  seedling  of  the 
Cluster  variety.  It  was  planted  about  1893.  The  variety  obtained  con- 
siderable fame  in  its  own  immediate  neighborhood  and  was  propagated 
there  quite  extensively  by  top-grafting  upon  native  black  walnuts  some 


Fig.   52. — Chase  walnut,  original  tree. 

time  before  it  was  exploited  in  a  popular  way.  Mr.  Ely  Hutchinson 
of  Concord  propagated  the  variety  quite  largely  on  his  place,  thus 
giving  it  a  thorough  test  in  that  locality.  It  was  taken  up  by  Mr. 
Leonard  Coates,  the  nurseryman,  about  1908  and  propagated,  adver- 
tised and  sold  quite  extensively  by  him  thereafter.  Not  yet  much 
tested  in  the  south.     One  of  the  first  descriptions  of  the  Concord  is 


264  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

found  in  an  article  by  Mr.  Coates  in  the  California  Cultivator  of  October 
7,  1909,  page  339. 

NUT. 
Size. 

Medium. 

Form. 

Broad  and  short,  with  a  square  cut  base  slightly  wider  than  the  apex 
in  most  specimens.  Apex  very  broadly  pointed.  Some  of  the  nuts 
slightly  elongated  and  somewhat  unsymmetrical  at  both  ends. 

Surface. 

Medium  smooth,  with  a  considerable  percentage  of  rather  rough  speci- 
mens. 

Color. 

Tan.  Lighter  than  most  of  the  southern  California  varieties,  but  a 
little  duller  than  San  Jose,  Franquette,  and  the  best  Mayettes. 

Uniformity. 

Fair.  A  considerable  proportion  of  the  nuts  rougher  and  more 
pointed  than  the  type.    There  is  also  a  considerable  variation  in  color. 

Cracking  Quality. 

Nuts  fairly  well  sealed,  but  cracking  in  the  fingers  without  much  diffi- 
culty. 

Pellicle. 

Very  light  and  attractive. 

Meat. 

Plump  and  well  formed,  filling  the  shell  very  completely. 

Flavor. 

Mild  and  free  from  any  decided  characteristic. 

TREE. 
Foliation  Period. 

Medium  late.  Decidedly  later  than  Placentia  Perfection,  but  consid- 
erably earlier  than  Franquette.  According  to  Mr.  Hutchinson,  it  is 
about  a  week  later  than  the  Placentia  and  three  weeks  earlier  than  the 
Franquette  in  his  locality.  In  the  south  there  is  considerably  more 
difference  than  this  between  the  Placentia  and  Franquette,  and  the  Con- 
cord is  apparently  nearly  intermediate  between  them.  Its  foliation 
period  is  very  nearly  the  same  as  that  of  Eureka.  The  foliage  is  held 
well  into  the  fall. 

Growth. 

Vigorous  and  rapid  in  the  case  of  young  grafts.  The  original  tree  is 
decidedly  small  for  its  age  and  the  apparently  favorable  conditions 
under  which  it  stands,  but  young  trees  or  grafts  observed  in  various 
parts  of  the  State  appear  to  be  particularly  thrifty  in  growth. 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  265 

Foliage. 

Abundant  and  vigorous,  persisting  in  good  condition  late  in  the  fall. 

Harvest  Season. 

Medium  or  fairly  early. 

Precocity. 

Apparently  fairly  good.  Considerably  more  precocious  than  Fran- 
quette  and  perhaps  less  so  than  Placentia  Perfection,  Chase  and  Prolific. 

Production   in  Older  Trees. 

The  possibilities  of  this  variety  as  to  permanent  production  cannot  be 
accurately  judged.  The  original  tree  is  rather  small,  and  its  production 
could  certainly  be  much  exceeded  by  well  grown,  grafted  trees.  Mr. 
Hutchinson 's  trees  consist  of  top  grafts  on  large  black  walnuts,  growing 
without  irrigation.  The  variety  is  probably  a  better  bearer  than  Fran- 
quette,  but  less  productive  than  some  of  the  southern  varieties.  More 
than  this  cannot  be  said  at  present.  The  possibilities  of  this,  like  all 
other  varieties,  will  probably  vary  to  a  considerable  extent  in  various 
parts  of  the  State. 

Susceptibility  to  Blight  and  Other  Troubles. 

The  Concord  has  been  advertised  as  being  especially  desirable  on 
account  of  immunity  to  blight.  On  account,  however,  of  the  very  slight 
extent  to  which  it  has  been  tested  in  this  respect,  we  do  not  feel  that  any 
statement  upon  this  matter  is  justified.  There  appears  to  be  consider- 
able doubt  as  to  the  extent  to  which  true  walnut  blight  exists  in  the 
original  locality  of  the  Concord,  and  in  any  event  it  is  certainly  one 
where  conditions  are  not  favorable  to  the  occurrence  of  this  disease. 
Being  late  in  coming  out  in  the  spring,  it  is  probable  that  the  Concord 
will  prove  considerably  free  from  blight  as  compared  with  earlier  varie- 
ties. In  respect  to  sunburn,  this  variety  appears  to  be  well  adapted  to  a 
hot,  sunny  region,  inasmuch  as  conditions  of  this  sort  exist  to  a  con- 
siderable extent  in  its  original  location  and  the  nuts  produced  there  are 
of  very  light  meat,  with  no  serious  discoloration  from  the  sun.  The 
foliage,  moreover,  is  abundant  and  thrifty,  affording  shade  to  the  nuts. 

GENERAL   REMARKS. 

The  Concord  is  perhaps  next  to  the  Franquette  the  best  tested  variety 
for  the  north  and  central  interior  portions  of  California.  In  Contra 
Costa  County  it  is  to  be  found  to  the  extent  of  several  hundreds  of  trees 
of  various  ages,  and  has  proven  itself  there  to  be  of  thrifty,  vigorous 
growth,  fair  quality,  and  a  regular  producer  of  satisfactory  crops.  It 
is  late  enough  in  coming  out  to  protect  it  to  a  considerable  extent  from 
frost  and  blight,  yet  not  extremely  late  in  maturing  its  crop  in  the  fall. 
Young  tr<.'es  make  a  quick,  vigorous  development  and  appear  to  be 
fairly  precocious  in  bearing.     The  nut  is  of  fairly  good  appearance 


266  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


Fig.  53. — Concord  walnut,  natural  size. 


Bulletin   2311  WALNUT    CULTURE    IN    CALIFORNIA. 


267J 


Fig.  54. — Concord  walnut,  natural  size. 


268 


UNIVERSITY    OP    CALIFORNIA— EXPERIMENT    STATION. 


and  of  decidedly  good  fullness  and  color  of  the  meat.  Against  the 
variety,  it  may  be  said  that  the  nuts  are  of  only  medium  or  even  rather 
small  size,  especially  as  the  trees  grow  older,  and  of  no  more  than 
average  quality  in  appearance.  For  the  southern  part  of  the  State  the 
Concord  has  not  been  sufficiently  tested  to  justify  any  positive  statement 


Fig.     55. — Concord    walnut,     original    tree. 

concerning  its  development  there.  For  the  north  it  is  reasonably  certain 
that  this  variety  will  make  a  vigorous,  quick-growing  tree,  producing 
good  commercial  crops,  of  full,  sweet-meated,  not  very  large  nuts,  within 
a  reasonable  time.  It  is  inferior  to  Franquette  in  size  and  quality  of 
the  nuts,  but  will  probably  surpass  it  in  production  and  precocity. 


Bulletin  2311  WALNUT    CULTURE    IN    CALIFORNIA.  269 

EUREKA. 
Origin. 

This  variety  originated  in  a  seedling  tree  on  the  Stone  ranch,  at 
present  owned  by  Mr.  William  Holve,  one  mile  south  of  Fullerton,  Cali- 
fornia. The  particular  tree  stands  directly  in  front  of  the  house  by 
the  roadside  and  is  one  of  a  group  of  about  six  trees  which  were  planted 
about  1890  or  earlier,  from  nuts  obtained  at  the  old  Meek  place,  near 
Hayward,  California.  The  parent  tree  was  one  of  the  Persian  or 
Kaghazi  type  which  we  have  described  under  that  name.  The  desir- 
able quality  of  this  tree  was  first  appreciated  by  Mr.  E.  G.  Ware,  of 
Garden  Grove,  who  named  the  variety  Stone's  Eureka,  about  1903.* 
Mr.  D.  C.  Disher  of  Garden  Grove  was  associated  with  Mr.  Ware  in 
first  propagating  and  calling  attention  to  the  merits  of  this  variety. 
Up  to  about  1909  very  few  Eureka  trees  were  propagated  except  by  Mr. 
Disher  and  almost  all  of  his  were  bought  by  Mr.  C.  W.  Lefnngwell, 
Jr.,  and  planted  on  his  ranch  at  East  Whittier.  Messrs.  Ware  and 
Disher  planted  a  few  on  their  places  at  Garden  Grove,  and  Mr.  J.  B. 
Neff  of  Anaheim  also  had  a  few  of  the  earlier  trees.  There  are  also  a 
very  few  of  these  on  some  of  the  ranches  in  the  vicinity  of  the  Stone 
place  where  the  variety  originated.  In  1909  Mr.  Neff  top-grafted 
about  200  orchard  trees,  mostly  Placentia  Perfection,  to  this  variety, 
and  the  Experiment  Station,  through  the  Whittier  Laboratory,  began 
sending  out  Eureka  scions  for  trial  to  all  parts  of  the  State.  In  1911 
several  nurserymen  began  listing  this  variety. 

NUT. 
Size. 

Large.      Average  1J  by  If.      Many  larger. 

Form. 

Decidedly  elongated,  with  parallel  sides;  apex  and  base  of  equal 
breadth,  or  a  little  thicker  at  the  apex.  Rather  rectangular  or  square 
in  end  view.  Nuts  very  blunt,  with  a  little  more  taper  at  the  base 
than  at  the  apex. 

Surface. 

Quite  smooth,  sutural  ridges  not  prominent  except  at  one  point  a 
little  toward  the  apex  from  the  middle. 

Color. 

Dull,  light  brown,  more  attractive  when  bleached  or  well  washed. 
Very  pleasing  to  the  eye  when  properly  bleached. 

Uniformity. 

Pronounced.  One  of  the  strong  qualities  of  the  variety.  Nut  easily 
distinguished  from  any  other  kind. 


*The  Pacific  Rural  Press  of  January  23,  1904,  contains  what  appears  to  be  the  first 
printed  mention  of  this  variety. 


270  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

Cracking  Quality. 

Shell  hard,  rather  thick,  heavy  and  very  strongly  sealed.  Never 
splitting  open  in  handling  and  not  easily  cracked  with  the  fingers. 
Meat  easily  extracted  after  cracking. 

Pellicle. 

Straw  color,  light  and  attractive. 

Meat. 

Full  and  heavy  in  good  specimens.  Averages  45  to  50  per  cent  of 
total  weight  of  nut,  while  the  shell  is  extra  heavy. 

Flavor. 

Excellent.       Particularly  sweet. 

TREE. 

Foliation  Period. 

Medium  late.  About  midway  between  the  early  blooming  varieties 
like  Chase  and  Placentia  Perfection  and  the  very  late  ones,  such  as 
Franquette.  A  little  later  than  Concord.  Earlier  in  the  north  than 
in  the  south. 

Growth. 

Extremely  vigorous  and  rapid,  especially  in  nursery  and  top  grafts. 
Young  trees  form  a  few  large  leaders,  with  few  fruit  spurs  until  the 
fourth  or  fifth  year.  The  smooth  bark  of  the  trunks  of  young  trees  has 
a  yellowish  color.  The  bark  on  the  trunk  of  the  older  trees  is  cracked 
or  furrowed  up  and  down  in  a  manner  characteristic  of  the  Kaghazi 
type. 

Foliage. 

Very  thrifty  and  abundant,  shading  the  nuts  well. 

Harvest  Season. 

A  little  later  than  that  of  the  earliest  varieties,  considerably  earlier 
than  Franquette. 

Precocity. 

Not  marked  in  southern  California.  About  two  years  later  than 
Chase,  Placentia  Perfection,  etc.,  in  coming  into  bearing.  Experience 
in  the  northern  part  of  the  State  indicates  that  Eureka  is  more  preco- 
cious there  than  in  the  south. 

Production   in  Older  Trees. 

Can  only  be  judged  from  the  original  tree.  This  was  said  to  be 
averaging  somewhat  over  200  pounds  of  nuts  per  year  when  sixteen 
to  eighteen  years  of  age,  before  being  heavily  cut  for  scions.  The  tree 
is  positively  known  to  us  to  have  borne  this  amount  in  at  least  one  or 
two  years.  From  the  oldest  propagated  trees  of  the  variety,  Mr.  E.  G. 
Ware  obtained  a  few  nuts  during  the  fifth  year  after  planting  and  as 
high  as  20  pounds  on  some  trees  during  the  seventh  year.     In  Mr.  C.  W. 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  271 

Leffingwell,  Jr.  's  grove  the  first  nuts  were  produced  in  the  fourth  year 
after  planting  and  only  a  very  few  trees  had  nuts  on  them  during  that 
year.  During  the  fifth  year  there  was  a  sprinkling  of  nuts  on  every 
tree,  but  hardly  enough  to  be  measured  in  pounds.  In  the  vicinity  of 
Stockton,  Eureka  top-grafted  on  good  sized  black  walnut  trees  by 
Dr.  W.  W.  Fitzgerald  produced  a  few  nuts  the  first  year  after  grafting 
and  quite  a  sprinkling  of  them  during  the  following  season.  Mr.  Ely 
Hutchinson  of  Concord  had  the  same  experience.  The  variety  has 
shown  a  wonderful  vigor  of  growth  wherever  tried  in  this  way. 

Susceptibility  to   Blight  and  Other  Troubles. 

From  all  experience  with  Eureka  we  are  justified  in  stating  that  this 
is  the  most  resistant  to  blight  of  any  variety  thus  far  observed.  That 
it  does  not  merely  escape  the  blight  by  late  blooming,  but  actually 
resists  it  to  a  considerable  extent  seems  to  be  the  case  from  the  fact 
that  still  later  blooming  varieties  are  more  susceptible  to  blight  than 
Eureka.  It  may  be  said  of  this  variety  that  it  has  been  very  thor- 
oughly tested  in  regard  to  blight  resistance,  which  is  not  the  case  with 
many  kinds  which  are  advertised  as  immune.  The  original  tree  stands 
in  a  locality  where  the  disease  has  prevailed  for  many  years  and  caused 
immense  losses.  The  tree  is  surrounded  on  all  sides  by  seedling  wal- 
nut groves  in  which  the  blight  has  occurred  at  its  worst.  The  state- 
ment, therefore,  that  no  sign  of  the  disease  has  ever  been  seen  on  this 
tree  seems  a  strong  one,  yet  if  not  absolutely  true,  it  is  certainly  a  fact 
that  year  after  year,  when  seedling  groves  all  about  were  very  badly 
blighted,  no  blight  could  be  found  upon  this  tree,  and  so  far  as  we  know 
in  five  years'  observation  it  has  never  been  affected  to  any  appreciable 
extent  by  the  disease.  "While  young  trees  planted  in  other  localities  and 
in  new  localities  may  possibly  lack  this  absolute  immunity  from  blight, 
it  is  certainly  true  that  the  Eureka  has  shown  the  greatest  freedom 
from  the  disease  under  the  most  severe  test  of  any  variety  which  is  now 
before  the  public.  In  this  respect  it  has  fully  justified  the  name  given 
to  it  by  Messrs.  Ware  and  Disher  nearly  ten  years  ago  in  their  search 
for  a  blight-resistant  variety.  In  respect  to  other  troubles  than  blight, 
the  Eureka  has  thus  far  been  entirely  free  from  perforation,  and  it  is 
not  likely  that  the  variety  will  ever  develop  this  trouble  on  account  of 
its  strong,  thick  shell.  It  is  also  free  from  sunburn  on  account  of 
its  abundant  foliage  and  thick  husk,  and  in  every  way  the  variety  is 
healthy,  thrifty,  and  free  from  disease. 

GENERAL   REMARKS. 

The  Eureka  comes  very  close  to  satisfying  the  requirements  of  an 
ideal  walnut  for  California.  It  is  a  fine,  large  nut  of  strikingly 
handsome  appearance,  extra  full  meat  and  weight,  perfectly  sealed, 


272  UNIVERSITY    OF    CALIFORNIA  — EXPERIMENT    STATION. 


Fig.   56. — Eureka  walnut,  natural  size. 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA. 


273 


W 

^9n                                                                                         .*  wH 

Ls 

Ji'                     lift                       s9h 

■  ,■.->■; 

^r     ^^IB 

1 

■:-:'M!'    W ' "              H  ^**^,                             • 

mM 

'iflr  M^m    W 

W-~Z%Tm 

_  MiiWiir.*-— tf^SW^B          ^^^^^^^E^.'  ~'<''W't^rw^--^2a£SCjMdHB 

WJ . 

A  ■ 

HP    «F   1 

Br-'                                            .9 

Fig.  57. — Eureka  walnut,  natural  size. 


11—231 


274 


UNIVERSITY    OF    CALIFORNIA  — EXPERIMENT    STATION. 


light-colored  meat,  fine  flavor,  marked  immunity  to  disease,  a  strong, 
vigorous  grower  and  ultimately  a  heavy  producer.  Its  worst  defect 
thus  far  has  been  a  tendency  toward  a  slightly  imperfect  development  of 
the  meat  in  certain  seasons,  especially  a  shriveling  of  the  meat  at  the 
basal  end  of  the  nut.  This  has  been  most  pronounced  during  dry  years, 
on  lighter  soils  and  on  trees  which  received  little  or  no  irrigation.  The 
same  shriveling  has  usually  occurred  at  the  same  time  in  other  varie- 


Fig.  58. — Eureka  walnut,  original  tree. 

ties.  The  variety  is  strong  as  compared  with  any  other  southern  Cal- 
ifornia kinds  in  its  freedom  from  blight  and  perforation,  extremely 
thrifty  foliage  and  growth,  large  size,  uniformity,  and  attractive 
appearance  of  the  nuts,  especially  when  bleached,  and  their  strong 
sealing  and  heavy  weight.  While  the  percentage  of  meat  is  slightly 
lower  than  in  Placentia  Perfection  and  a  few  other  varieties,  this  is 
not  due  to  a  lesser  amount  of  meat,  but  rather  to  the  greater  weight  of 


Bulletin  231 


WALNUT    CULTURE    IN    CALIFORNIA. 


275 


the  shell;  in  other  words,  Eureka  nuts  are  heavier  than  those  of  the 
same  size  of  any  other  variety,  thus  making  fewer  nuts  per  pound 


Fig.  59. — Eureka  walnut  tree,  three  years  old. 

or  more  pounds  per  sack.  Compared  with  Franquette  or  any  other 
French  variety  or  California  variety  of  French  origin,  Eureka  is  a 
more  precocious  and  heavier  bearer,  more  thrifty  in  growth  and  foli- 


276 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


age,  equally  proof  against  ordinary  spring  frosts  by  lateness  in  its 
foliation  period,  and  considerably  earlier  in  maturing  its  nuts  in  the 
fall.     In  the  south  it  is  less  precocious  than  the  best  southern  varie- 


Fig.   60. — Eureka  walnut  tree,  six  years  old. 


ties,  but  promises  ultimately  to  exceed  most  of  them  in  production. 
In  the  north  it  seems  as  precocious  as  any  variety  yet  tested  commer- 
cially. The  size  of  its  nuts  is  well  sustained,  contrary  to  the  case  in 
some  of  the  other  varieties.     From  present  information  this  variety 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  277 

appears  especially  promising  in  the  northern  part  of  the  State,  and 
the  expectation  is  well  justified  that  Eureka  may  become  the  best  va- 
riety for  the  northern  districts.  In  the  south  the  variety  has  disap- 
pointed some  on  account  of  its  slowness  in  bearing  as  compared  with 
Placentia  Perfection,  but  it  is  significant  that  those  who  have  known 
the  variety  best  and  longest,  walnut  growers  of  the  immediate  locality 
of  the  original  tree,  are  very  enthusiastic  about  the  Eureka  and  express 
themselves  very  strongly  in  its  favor.  In  all  events,  present  knowl- 
edge seems  to  indicate  the  particular  adaptability  of  this  variety  to 
the  northern  part  of  the  State  and  to  fairly  heavy,  well  irrigated  land. 

FRANQUETTE. 

Origin. 

A  French  variety  said  to  be  nearly  two  hundred  years  old.  First 
introduced  into  California  by  Felix  Gillet  in  1871.  Most  of  the  Fran- 
quettes  at  present  growing  in  the  State  have  been  derived  from  Gillet 's 
importations,  although  the  variety  has  possibly  been  brought  from 
France  by  others  in  one  or  two  instances.  The  present  standing  of  the 
Franquette  as  the  leading  northern  California  and  Oregon  variety  is 
based  on  the  success  of  the  Vrooman  grove  at  Santa  Rosa.  This  sixty- 
acre  walnut  orchard  was  planted  by  the  late  Mrs.  Emily  Vrooman  at 
a  time  when  commercial  walnut  growing  north  of  Santa  Barbara  County 
was  absolutely  unknown,  and  as  a  result  of  Mrs.  Vrooman 's  investigation 
of  and  confidence  in  the  Franquette  the  qualities  of  this  variety  are 
well  established.  In  more  recent  years  the  Franquette  has  been  exten- 
sively taken  up  by  the  Leibs  of  San  Jose,  who  have  become  the  leading 
exponents  of  this  variety.  Through  the  influence  of  the  Oregon  Nursery 
Company,  who  bought  the  scions  and  nuts  from  the  Vrooman  orchard 
for  a  period  of  several  years,  the  fame  and  popularity  of  the  Fran- 
quette have  been  largely  extended  and  many  others  have  become  familiar 
with  and  planted  the  Franquette  on  a  considerable  scale,  both  in 
central  and  northern  California  and  Oregon.  In  southern  California 
there  is  a  large  tree  on  the  old  Experiment  Station  grounds  near 
Pomona,  Mr.  Neff  of  Anaheim  has  a  few  trees  top-grafted  to  Fran- 
quette, and  there  are  several  young  and  top-grafted  trees  at  the  Whit- 
tier  laboratory  and  at  the  Pasadena  City  Farm. 

NUT. 
Size. 

Medium  to  large.    Well  sustained  on  old  trees. 

Fcrm. 

Decidedly  elongated  and  pointed.    Base  much  broader  than  apex. 

Surface. 

Medium  smooth.    Sutural  ridges  quite  prominent. 


278  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

Color. 

Light  yellowish  brown. 

Uniformity. 

Strong.  The  uniform  and  characteristic  shape  of  the  Franquette 
nuts  makes  them  easier  to  identify  than  those  of  almost  any  other 
variety. 

Cracking   Quality. 

Nuts  strongly  sealed,  but  quite  thin  shelled  so  that  they  are  readily 
cracked. 

Pellicle. 

Pale  yellowish  tan,  giving  the  meat  a  very  light  colored,  attractive 
appearance. 

Meat. 

Moderately  plump  and  filling  the  body  of  the  shell  fairly  well.  The 
shell  is  considerably  longer  than  the  meat,  leaving  a  hollow  space  within 
the  apical  point  of  the  nut. 

Flavor. 

Sweet  and  free  from  bitterness,  with  a  characteristic  nutty  flavor  ap- 
proaching that  of  a  hickory  nut.  The  consistency  of  the  meat  is  also 
characteristic,  being  unusually  soft  or  oily. 

TREE. 
Foliation  Period. 

Very  late.  The  latest  of  any  important  variety  in  California.  Often 
two  to  three  months  later  in  coming  out  in  the  spring  than  the  earliest 
varieties.  The  Franquette  is  also  noticeably  early  in  dropping  its 
foliage  in  the  fall  so  that  its  seasonal  period  of  growth  is  comparatively 
short. 

Growth. 

Fairly  vigorous  and  rapid,  but  decidedly  less  so  than  that  of  many 
other  varieties.  The  best  growth  of  the  Franquette  is  seen  in  compara- 
tively cool,  moist  localities,  as  for  instance  in  the  coastward  region  of  the 
central  and  northern  parts  of  the  State.  In  the  south  and  in  the  inte- 
rior, especially  without  irrigation,  the  Franquette  is  of  slower  growth. 

Foliage. 

Abundant  and  thrifty,  but  developed  late  and  shed  early  in  the  season. 

Harvest  Season. 

Late.    One  of  the  undesirable  features  of  this  variety. 

Precocity. 

Not  pronounced.  The  Franquette  is  one  of  the  slowest  in  coming  into 
bearing. 

Production  in  Older  Trees. 

So  far  as  can  be  judged  by  the  oldest  Franquette  trees  in  the  State 
the  Franquette  is  a  regular  and  consistent  but  not  a  heavy  bearer.    Trees 


Bulletin   231]  WALNUT    CULTURE    IN    CALIFORNIA.  279 

ten  to  fifteen  years  of  age  have  averaged  not  over  40  pounds  per  year 
and  100  pounds  is  probably  a  maximum  production  for  large,  mature 


Fig.   CI. — Franquette  walnut,  natural  size. 


trees  of  this  variety.    Groves  of  nursery-grafted  trees  in  their  sixth  year 
after  planting  have  scarcely  averaged  10  pounds  per  tree. 


280  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


Fig.  62. — Franquette  walnut,  natural  size. 


Bulletin  231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


281 


Susceptibility  to   Blight  and  Other  Troubles. 

The  Franquette  is  noticeably  free  from  blight  in  most  cases  on  account 
of  its  extreme  lateness  in  coming  out  in  the  spring.  The  variety  appears 
to  have  very  little  actual  resistance  to  the  disease,  since  in  foggy  locali- 
ties the  nuts  and  twigs  sometimes  blight  quite  badly.  The  thick  husk 
and  abundant  foliage  protect  the  nuts  from  sunburn  to  a  very  large 
extent,  and  the  variety  is  not  especially  susceptible  to  any  other  trouble, 
except  that  in  some  years  the  meat  shrivels  rather  badly. 


Fig.   63. — Franquette  walnuts,  Vrooman  grove. 


GENERAL  REMARKS. 

The  Franquette  is  undoubtedly  our  best  proven  variety  for  central 
and  northern  California  and  has  one  great  advantage  over  any  other 
variety  for  that  section,  that  it  has  been  thoroughly  tested  and  its  merits 
and  demerits  well  established.  It  is  thus  possible  to  judge  the  variety 
more  critically  than  can  be  done  with  any  other  northern  variety,  and 
for  this  reason  our  description  of  it  may  sound  more  unfavorable 
than  the  Franquette  really  merits.    As  regards  quality  of  the  nut,  this 


282 


UNIVERSITY    OF    CALIFORNIA  — EXPERIMENT    STATION. 


variety  may  be  taken  as  a  standard,  as  it  is  undoubtedly  the  best  of  any 
variety  which  has  been  widely  tested  in  California.  Its  characteristic 
and  uniform  shape,  light,  attractive  color,  both  of  shell  and  meat,  firm 
sealing  yet  easy  cracking  quality,  and  the  particularly  pleasing  flavor 


and  consistency  of  the  meat  all  go  to  make  the  Franquette  nut  one  of 
the  very  highest  quality.  The  variety  is  also  strong  in  freedom  from 
blight  and  spring  frost  injury  on  account  of  its  very  late  season  of  com- 
ing out.     The  most  prominent  faults  of  the  variety  are  its  slowness  in 


BULLETIN   231 J  WALNUT    CULTURE    IN    CALIFORNIA.  283 

coming  into  bearing,  the  late  period  of  maturity  of  the  nuts  in  the  fall, 
and  the  fact  that  the  tree  is  by  no  means  as  heavy  a  bearer  as  should  be 
looked  for  in  an  ideal  variety.  All  in  all,  then,  we  may  say  that  the 
Franquette  is  a  variety  of  unusually  high  quality  and  rather  poor  pro- 
duction. For  southern  California,  where  it  has  been  tested  to  some 
extent,  we  do  not  believe  that  this  or  any  other  extremely  late  variety 
is  to  be  considered.  Farther  north  it  is  undoubtedly  true  that  for  the 
ultra-conservative  planter,  at  least,  no  other  variety  can  be  considered 
as  safe  as  this,  since  its  behavior  in  orchard  form  can  be  very  closely 
forecasted.  Franquette  nuts  have  commonly  sold  for  nearly  twice  the 
price  of  southern  California  seedlings,  which  offsets  to  some  extent  the 
light  bearing  and  lack  of  precocity  of  the  variety. 

PLACENTIA. 

(Placentia   Perfection.) 
Origin. 

Originated  in  Placentia,  near  Fullerton,  California,  as  a  seedling  of 
the  Santa  Barbara  Soft  Shell  type.  The  original  tree  stood  in  an 
orchard  of  Geo.  Hind  &  Company,  about  one  mile  north  of  the  Placentia 
schoolhouse ;  the  first  propagation  of  the  variety  was  done  by  Mr.  Hind 
about  1893,  and  the  variety  received  its  name  from  this  gentleman. 
Mr.  J.  B.  Neff  of  Anaheim  was  the  first  to  plant  any  considerable  acre- 
age of  Placentia  Perfections,  the  first  trees  which  he  bought  of  Hind 
&  Company  being  bench-grafted  on  piece  roots,  using  about  six  to  ten 
inches  of  the  root  and  making  three  to  four  nursery  trees  from  one  root. 
In  former  years  Mr.  Neff  sold  many  scions  and  seed  of  this  variety  to 
nurserymen  over  the  State,  as  much  as  1,600  pounds  of  nuts  and  20,000 
scions  in  one  season.  In  later  years  he  refused  to  sell  either  seed  for 
planting  or  scions,  on  account  of  the  susceptibility  of  this  variety  to 
walnut  blight.  He  also  grafted  over  all  his  younger  Placentia  trees  to 
the  Eureka  variety  on  account  of  the  blight. 

At  present  there  seem  to  be  in  southern  California  two  fairly  distinct 
types  of  the  Placentia  walnut,  even  among  trees  which  are  supposed  to 
have  been  grafted  from  pure  stock.  These  two  types,  while  in  most 
respects  identical,  differ  in  that  the  nut  of  one  is  quite  elongated  while 
the  other  has  a  decidedly  round  nut.  The  quality  of  the  nut  in  the  two 
types  is  apparently  identical,  as  well  as  the  general  characteristics  of 
the  tree.  Mr.  Neff's  trees,  which  are  certainly  of  the  purest  original 
strain,  bear  nuts  of  the  round  type,  but  the  majority  of  the  younger 
groves  of  this  variety  in  southern  California  bear  the  longer  type  of  nut, 
which  is  that  which  we  are  about  to  describe.  This  latter  type  is  more 
variable  in  form  and  smoothness  of  the  nuts  than  the  other.  That  this 
variation  has  occurred  in  the  grafted  progeny  of  one  original  tree  rather 
than  by  mixing  of  the  stock  seems  very  possible,  as  the  different  types 
are  too  much  alike  to  be  considered  entirely  distinct  varieties. 


284  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

NUT. 
Size. 

Medium,  averaging  1£  by  1J  by  1J  inches.  Runs  largely  to  average 
size,  with  few  very  large  or  very  small  nuts. 

Form. 

Regular,  oval,  somewhat  elongated;  base  and  apex  nearly  equal  in 
breadth.  Flattened,  with  greater  diameter  at  right  angles  to  the 
sutures. 

Surface. 

Quite  smooth.    Sutural  ridges  not  especially  prominent. 

Color. 

Light  neutral  brown,  mottled  with  gray,  giving  the  nut  a  distinctly 
pinkish  cast. 

Uniformity. 

Not  especially  strong.  Nuts  quite  uniform  in  size,  but  varying  consid- 
erably in  shape  and  smoothness.  Some  quite  elongated,  others  nearly 
round,  some  quite  rough. 

Cracking  Quality. 

Nuts  poorly  sealed,  causing  them  to  open  very  readily  between  the 
fingers  or  when  exposed  to  the  sun.  Shell  thin  and  strong.  Septum 
almost  free  from  the  shell,  so  that  the  nut  can  be  very  easily  opened 
with  the  fingers  and  the  whole  meat  taken  out  intact. 

Pellicle. 

Light  tan  colored,  or  very  light  silvery  brown,  with  a  glossy,  waxed 
appearance.    Decidedly  attractive. 

Meat. 

Quite  smooth,  with  comparatively  few  convolutions.  Uniformly 
plump  and  full,  averaging  fully  50  per  cent  or  slightly  more  of  the  total 
weight  of  the  nut. 

Flavor. 

Mild  and  pleasant,  with  no  pronounced  character. 

TREE. 
Foliation  Period. 

Quite  early.  Nearly  two  weeks  later  than  Chase  and  the  average  of 
the  Santa  Barbara  Soft  Shell  seedlings.  From  one  to  four  weeks  earlier 
than  Concord  and  Eureka. 

Growth. 

Vigorous,  making  a  large,  tall  tree,  the  more  erect,  taller  branches 
standing  up  from  the  lower  portion  in  a  characteristic  manner. 

Foliage. 

Very  abundant  and  thrifty. 

Harvest  Season. 

Early. 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  285 

Precocity. 

Fair.  Commences  bearing  fairly  well  while  qnite  young,  at  least  in 
southern  California. 

Production  in  Older  Trees. 

Very  good,  but  not  exceptionally  heavy,  so  far  as  can  be  learned  from 
present  plantings. 

Susceptibility  to   Blight  and  Other  Troubles. 

Badly  affected  by  blight  under  conditions  favorable  to  the  disease. 
Nuts  sometimes  badly  perforated,  especially  on  young  trees.  Otherwise, 
not  especially  susceptible  to  disease. 

GENERAL   REMARKS. 

The  Placentia  Perfection  is  in  many  respects  the  best  walnut  which 
has  yet  been  thoroughly  tried  in  southern  California,  and,  all  things  con- 
sidered, is  entitled  to  be  called  the  best  proven  variety  for  that  part  of 
the  State.  It  comes  close  to  being  an  ideal  nut  save  for  two  defects,  but 
these  are  so  great  as  to  preclude  all  idea  of  considering  it  a  thoroughly 
satisfactory  variety.  These  defects  are  the  poor  sealing  of  the  nuts  and 
the  susceptibility  of  the  variety  to  blight.  The  nuts  crack  open  badly 
in  ordinary  handling,  and  still  more  so  if  exposed  to  the  sun  to  any 
extent  in  drying.  In  regard  to  blight,  the  Placentia  Perfection  is  very 
susceptible  to  the  disease,  which  again  belies  its  name.  Aside  from  these 
two  defects,  however,  the  variety  is  one  of  high  quality  and  is  probably 
unequaled  by  any  other  as  a  commercial  walnut  for  southern  Cali- 
fornia. It  is  of  a  desirable  and  attractive  form  and  size,  heavy  and 
very  plump  meat  running  a  full  50  per  cent  or  better.  The  meat  is  of  a 
very  attractive  color  and  appearance  and  can  easily  be  taken  out  of  the 
shell  whole  with  the  fingers.  The  nuts  are  almost  invariably  well  filled, 
even  in  seasons  when  the  average  quality  of  walnuts  in  this  respect  is 
very  poor.  The  tree  is  thrifty  and  vigorous,  one  of  the  easiest  to  propa- 
gate by  grafting,  quite  precocious,  and  becoming  large  and  well  formed 
while  still  comparatively  young.  In  regard  to  production,  the  variety  is 
not  old  enough  to  be  critically  judged.  Trees  in  their  fifth  year  from 
planting  in  the  orchard  have  produced  from  twelve  to  twenty  pounds 
of  nuts,  which  is  as  good  as  almost  any  other  variety  will  average,  and 
better  than  most.  We  know  of  one  grove  which  produced  slightly  more 
than  one  ton  of  nuts  per  acre  in  its  tenth  year,  which  is  a  very  satisfac- 
tory yield  compared  with  present  groves,  although  by  no  means  up  to 
the  possibilities  of  an  ideal  variety.  Since  the  Placentia  has  no  im- 
munity to  blight  and  is  superior  only  in  the  quality  of  the  nut  and  satis- 
factory development  of  the  tree,  it  is  probable  that  varieties  will  be 
found  among  our  present  seedling  trees  equally  good  in  these  respects 
and  at  the  same  time  less  subject  to  the  defects  mentioned.  The 
Placentia  Perfection  is  usually  looked  upon  in  southern  California  at 


286 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


the  present  time  as  representing  the  best  type  of  commercial  walnut  in 
thai  section. 

The  variety  has  not  been  much  tested  outside  of  Orange  and  Los 


Fig.    65. — Placentia  walnut,   natural   size. 


Angeles  counties.    In  the  central  and  northern  portions  of  the  State  no 
experience  is  available  upon  which  to  base  an  opinion  as  to  its  merits 


Bulletin  2311 


WALNUT    CULTURE   IN    CALIFORNIA. 


287 


Fig.   66. — Placentia  walnut,    natural   size. 


•_>> 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 


Fig.   67. — Five-year-old   Placentia   tree   on   southern   California  black   root. 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  289 

or  the  advisability  of  planting  it  in  those  localities.  It  certainly  should 
not  be  planted  in  localities  where  the  blight  is  very  prevalent,  on  account 
of  fog  and  moisture  in  the  spring  and  early  summer.  Farther  inland,  as 
for  instance  in  the  Mount  Diablo  country  and  the  dryer  portions  of  the 
other  coast  valleys,  and  in  the  Sacramento  and  San  Joaquin  valleys  as 
far  as  walnut  culture  may  prove  feasible,  the  variety  is  worthy  of  con- 
siderable consideration,  especially  in  regions  not  too  much  subject  to 
late  spring  frosts.  In  the  latter  case  the  Placentia  probably  blooms  too 
early  to  be  worthy  of  consideration.  There  are  a  few  young  trees  of  the 
variety  in  the  northern  portion  of  the  State,  but  they  are  scarcely  old 
enough  to  be  critically  judged.  In  growth  and  general  development 
they  are  doing  very  well  but  have  not  yet  begun  to  fruit  abundantly. 
Given  freedom  from  late  frosts  and  conditions  not  too  favorable  to 
blight,  there  is  no  apparent  reason  why  the  Placentia  should  not  do  as 
well  in  the  north  as  in  the  south. 

PROLIFIC. 

(Disher's  Prolific,   Ware's  Prolific.) 
Origin. 

This  variety  originated  in  a  Santa  Barbara  Soft  Shell  seedling  tree 
at  Garden  Grove,  Orange  County,  California,  which  was  selected  by  Mr. 
D.  C.  Disher  as  being  worthy  of  propagation.  According  to  Mr.  E.  G. 
Ware,  who  was  closely  associated  with  Mr.  Disher,  the  tree  was  first 
selected  on  account  of  the  desirable  form  and  size  of  the  nuts  rather 
than  for  the  quantity,  which  the  present  name  of  the  variety  implies. 
It  was  found,  however,  that  after  young  trees  planted  in  orchard  form 
came  into  bearing  they  had  a  pronounced  tendency  toward  early  and 
heavy  bearing,  from  which  the  present  name  of  the  variety  is  derived. 
Mr.  Disher  propagated  a  considerable  number  of  trees  of  this  variety, 
mostly  by  budding  on  the  southern  California  black  root,  and  they 
have  been  planted  in  orchard  form  to  some  extent,  the  oldest  being  now 
in  about  their  sixth  year  since  planting  in  the  orchard.  Mr.  C.  W.  Lef- 
fingwell,  Jr.,  has  a  considerable  number  of  the  trees  upon  his  ranch  at 
East  Whittier,  Mr.  "Ware  has  five  acres  of  six-year-old  trees,  and  there 
are  a  few  other  orchard  plantings  of  this  variety  in  the  southern  part 
of  the  State.  The  variety  has  also  been  recently  introduced  into  the 
north,  but  cannot  yet  be  judged  in  that  part  of  the  State. 

NUT. 
Size. 

Rather  large  on  all  the  young  trees  of  this  variety  and  apparently 
well  sustained  on  the  original  tree. 

Form. 

Oval,  quite  elongated  and  decidedly  symmetrical.    Base  and  apex  of 
equal  breadth,  very  obtusely  pointed  at  both  ends. 
12—231 


290  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


Fig.  68. — Prolific  walnut,  natural  size. 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  291 

Surface. 

Quite  smooth,  with  several  quite  conspicuous  longitudinal  seams  or 
grooves  which  give  the  variety  a  characteristic  appearance. 

Color. 

Dull  light  brown,  requiring  bleaching  for  the  best  appearance. 

Uniformity. 

Quite  strong,  both  in  size,  shape  and  surface. 

Cracking   Quality. 

Poorly  sealed  at  the  apex,  so  that  the  nuts  open  easily. 

Pellicle. 

Amber  to  dark  brown,  or  in  many  cases  nearly  black  after  exposure 
to  rain.    The  weakest  quality  of  this  variety. 

Meat. 

Decidedly  plump  and  well  filled,  averaging  a  full  50  per  cent.  Equal 
to  the  best  in  this  respect. 

Flavor. 

Mild  and  pleasant.    Sometimes  rather  musty  after  exposure  to  rain. 

TREE. 
Foliation  Period. 

Early.  Not  later  than  the  average  of  the  Santa  Barbara  Soft  Shell 
seedlings. 

Growth. 

Fairly  vigorous,  with  a  strong  tendency  toward  the  formation  of 
fruiting  wood,  making  a  low,  spreading  tree,  with  a  few  straggling, 
upward-growing  leaders.  Very  numerous  fruit  spurs  develop  all  over 
the  tree  as  soon  as  it  is  established  in  the  orchard. 

Foliage. 

Abundant  and  thrifty. 

Harvest  Season. 

Early. 

Precocity. 

The  strongest  of  any  well  tested  variety.  During  the  first  ten' years 
in  the  orchard  will  probably  produce  at  least  twice  as  many  nuts  as  any 
other  southern  variety  and  many  times  more  than  any  of  the  French 
varieties  or  their  derivatives. 

Production  in  Older  Trees. 

The  original  tree  of  this  variety  stood  in  a  grove  of  Santa  Barbara 
Soft  Shell  seedlings  and  was  not  selected  as  being  a  tree  of  unusually 
heavy  production.  The  chief  merit  of  the  Prolific  in  regard  to  produc- 
tion appears  to  be  its  decided  tendency  toward  heavy  bearing  from 
about  the  third  to  the  tenth  year  in  the  orchard  as  compared  to  other 
varieties.    Mr.  Ware 's  grove  averaged  about  20  pounds  of  nuts  per  tree 


292 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


the  fifth  year  and  1,000  pounds  of  dried  nuts  per  acre  in  the  sixth 
season  after  planting  in  the  orchard,  which  crops  may  be  considered  ex- 
tremely satisfactory.     A  tree  of  our  own,  likewise  in  its  sixth  year, 


Fig.  69. — Prolific  walnut,  natural  size. 

produced  35  pounds  of  nuts,  whereas  our  best  Placentia  Perfection 
of  the  same  age  and  nearly  twice  as  large  as  the  Prolific  tree  produced 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA. 


293 


Fig.   70.— Four-year-old  Prolific  walnut  tree.     Note  abundant  fruit  spurs. 


294 


UNIVERSITY    OF    CALIFORNIA  — EXPERIMENT    STATION. 


less  than  20  pounds.     The  heavy,  early  bearing  of  this  variety  is  well 
established. 


Susceptibility  to   Blight  and  Other  Troubles. 

This  variety  has  no  particular  resistance  to  blight  but  is  affected  by 
the  disease  as  badly  as  the  average  of  our  soft-shell  seedlings.  It  is  also 
of  about  average  quality  as  regards  sunburn  and  other  injurious  in- 
fluences. 


Bulletin  231]  WALNUT    CULTURE   IN    CALIFORNIA.  295 

GENERAL    REMARKS. 

The  Prolific  is  worthy  of  special  consideration  on  account  of  jts 
marked  precocity  in  bearing.  This  does  not  mean  simply  the  production 
of  a  few  nuts  by  trees  in  the  nursery  or  soon  after  planting,  but  more 
than  this  it  is  well  established  that  this  variety  will  come  into  commercial 
bearing  within  three  years  after  planting  in  the  orchard  and  by  the 
sixth  or  seventh  year  will  turn  off  as  many  nuts  as  may  be  reasonably 
expected  from  old,  mature  trees  of  some  of  our  most  prominent  varieties. 
The  nut  is  of  excellent  size  and  shape,  but  badly  handicapped  on  account 
of  its  poor  sealing,  dark  colored  meat  and  susceptibility  to  blight.  On 
these  accounts  it  cannot  be  considered  an  ideal  variety  for  permanent 
planting.  It  is  particularly  worthy  of  consideration  for  interplanting 
with  such  varieties  as  the  Franquette,  Eureka,  or  even  Placentia  Per- 
fection. It  should,  however,  be  remembered  that  for  the  northern  part 
of  the  State  the  variety  has  not  been  tested  and  therefore  its  adaptability 
for  interplanting  with  Franquette  in  that  region  cannot  be  positively 
stated.  If  its  quality  of  heavy,  early  bearing  is  carried  out  in  the  north 
as  in  the  south  there  is  no  question  that  this  variety  would  pay  all 
expenses,  including  the  purchase  price  of  the  land,  while  Franquette  was 
coming  into  bearing. 

SAN   JOSE. 

(San  Jose   Mayette;  Wiltz.) 
Origin. 

This  is  a  Mayette  seedling  propagated  by  Felix  Gillet  and  planted 
near  San  Jose  some  years  ago.  The  variety  was  first  taken  up  by  Mr. 
Rudolph  Wiltz  of  San  Jose  and  afterward  extensively  advertised  and 
sold  by  Mr.  Leonard  Coates.  One  of  the  first  public  notices  of  the 
variety  is  found  in  the  Pacific  Rural  Press  of  January  26,  1907,  where 
Mr.  Wiltz  gives  the  name  San  Jose  to  this  variety.  Mr.  Gillet  also  has 
an  article  in  the  same  number  upon  the  same  subject. 

NUT. 
Size. 

Large;  decidedly  above  the  average  of  most  varieties,  although  not 
of  abnormally  large  size. 

Form. 

Rounded,  oval,  slightly  elongated,  very  symmetrical. 

Surface. 

Quite  smooth,  with  rather  few  quite  conspicuous  seams  and  veins. 

Color. 

Bright  yellow  tan.    Unusually  light  and  attractive  without  bleaching. 

Uniformity. 

Strong.    Nuts  easy  to  identify  by  their  shape,  size  and  color. 


296  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 


Fig.   72. — San  Jose  walnut,  natural  size. 


Bulletin  231 


WALNUT    CULTURE    IN    CALIFORNIA. 


297 


Fig.   73. — San  Jose  walnut,  natural  size. 


298  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

Cracking  Quality. 

Nuts  poorly  sealed  and  very  thin  shelled,  opening  easily  in  the  fingers. 

Pellicle. 

Light   colored  and  attractive. 

Meat. 

Rather  small  in  proportion  to  the  shell  and  poorly  developed. 

Flavor. 

Mild.     Not  pronounced. 

TREE. 

Foliation   period. 

Quite  late,  but  earlier  than  Franquette. 

Growth. 

Slow  and  not  particularly  vigorous. 

Foliage. 

Rather  sparse. 

Harvest  Season. 

Medium. 

Precocity. 

Not  well  tested. 

Production   in  Older  Trees. 

No  information  is  available  upon  this  point,  except  that  obtained  from 
Mr.  Wiltz'  place  where  the  trees  are  of  various  ages  and  top-worked  on 
black  walnuts  of  various  sizes.  It  is  evident,  however,  that  the  variety 
is  not  a  heavy  bearer. 

Susceptibility  to   Blight  and  Other  Troubles. 

The  San  Jose  has  not  been  widely  tested  in  this  respect,  yet  its 
behavior  in  respect  to  blight  can  probably  be  accurately  estimated  on 
account  of  the  favorable  conditions  for  disease  in  the  locality  where  the 
variety  originated.  On  Mr.  Wiltz'  place  it  appears  to  be  decidedly  free 
from  blight,  even  compared  with  the  Franquette  which  is  later  in  coming 
out.  "We  have  little  doubt  but  that  the  San  Jose  will  prove  decidedly 
free  from  blight  in  any  portion  of  the  State.  As  regards  sunburn  and 
other  unfavorable  climatic  and  soil  influences,  the  variety  is  rather  less 
promising  on  account  of  its  slow  growth  and  sparse  foliage.  The  nuts 
ere  quite  susceptible  to  perforation. 

GENERAL   REMARKS. 

It  is  to  be  said  to  the  credit  of  the  San  Jose  variety  that  it  is  without 
doubt  the  most  attractive  and  handsome  of  any  walnut  which  has  thus 
far  been  brought  forward  in  California.  Its  large  size,  pleasing  shape, 
and  particularly  its  bright,  yellowish-tan  color,  even  when  not  bleached 
or  even  washed,  makes  it  a  most  attractive  nut  and  one  which  is  in- 
variablv  selected  at  first  sight  from  all  others,  when  in  their  natural 


Bulletin  231]  WALNUT    CULTURE    IN    CALIFORNIA.  299 

condition.  For  a  few,  extra  handsome  walnuts  of  average  quality  we 
have  no  variety  at  present  equal  to  this.  As  a  commercial  nut,  however, 
little  more  can  be  said  in  its  favor.  The  tree  is  of  slow  growth  and 
scanty  foliage,  a  light  producer,  and  the  nuts  are  extremely  light  in 
proportion  to  their  size,  poorly  sealed,  snseeptible  to  perforation  or 
poorly  formed  shells,  and  with  small,  poorly  developed  meats. 

OPINION    OF   AN    EXPERT   WALNUT   BUYER. 

Samples  of  all  these  varieties  were  submitted  to  the  head  buyer  for 
one  of  the  largest  fancy  grocery  firms  in  California  for  his  opinion  as  to 
their  relative  merits.  This  gentleman  had  already  expressed  himself  in 
regard  to  the  Placentia  as  follows:  "The  nut  we  have  found  most  sat- 
isfactory is  the  Placentia.  This  variety  combines  good  size,  handsome 
appearance,  good  quality,  good  color  and  full  meat."  There  would  be 
little  question  of  the  all-round  superiority  of  this  variety  over  any  other, 
for  southern  California  at  least,  were  it  not  for  its  blighting  and  poor 
sealing  qualities.  Fair  samples  of  the  following  varieties  were  submitted 
to  the  expert,  each  under  number  rather  than  by  name:  1,  Eureka; 
2,  Franquette;  4,  San  Jose;  5,  Concord;  6,  Disher's  Prolific;  7,  Chase; 
8,  El  Monte.  His  opinion  follows:  "Numbers  1,  2  and  8  are  the  finest 
nuts  in  the  assortment,  although  it  is  very  difficult  to  say  which  might 
be  the  best  of  the  three  for  the  reason  that  all  possess  some  qualities 
which  the  others  lack.  For  instance :  No.  1  has  a  very  handsome  shell, 
a  good  fat  kernel  with  exceptionally  fine  flavor,  but  the  meats  tend 
slightly  toward  a  brown  shade.  No.  2  has  a  handsome  shell  but  the 
kernel  is  not  so  fat  as  in  No.  1,  although  the  color  of  the  meat  is  very 
good  and  the  flavor  excellent.  No.  8  is  not  so  handsome  in  appearance 
but  the  kernel  is  fat  with  good  flavor  but  meat  slightly  brown.  We 
believe,  taking  all  things  into  consideration,  that  No.  1  has  the  most  good 
points  and  if  this  variety  bears  well  it  would  undoubtedly  be  a  big 
success.  No.  4  has  the  advantage  of  a  thin  shell,  although  this  tends  to 
perforation  and  wTe  notice  that  the  shell  is  not  well  filled,  although  the 
meat  has  a  good  appearance  and  flavor.  No.  5  can  hardly  be  compared 
with  the  others.  This  nut  is  more  like  the  ordinary  seedling  nut  which 
has  been  on  the  market  for  many  years,  although  of  a  better  quality 
than  the  average.  No.  6  we  find  very  similar  to  No.  1.  This  nut  is  very 
symmetrical  in  appearance,  having  a  full,  fat  kernel  but  not  quite  so 
good  a  flavor  as  No.  1,  while  the  meat  is  quite  brown.  No.  7  is  good  as 
far  as  size  and  quality  of  meat  is  concerned  but  in  appearance  not  so 
good  and  the  meat  is  too  dark.  Now  to  take  all  things  into  considera- 
tion we  would  rate  these  nuts  in  the  following  way :  Nos.  1,  2,  8,  6,  4,  7, 
5."  It  should  be  understood  that  this  gentleman  passed  simply  on  the 
quality  of  the  nuts,  without  considering  the  producing  or  other  quali- 
ties of  the  tree. 


300 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 


Size  and  weight  of  average  specimens  of  principal  walnut  varieties.     WeigJit  in  grams. 
Volume  in  cubic  centimeters.     Dimensions  in  inches. 


Variety. 


Weight. 

Volume. 

12 

19 

11 

17.5 

14.5 

22 

14.5 

22 

12 

20 

13.5 

21 

14.5 

21.5 

10.8 

19 

12 

20 

11.1 

25 

25 

50 

13 

18 

11 

18 

Dimensions. 


Number 

per 
pound. 

Per  cent 
meat. 

38 

47 

42 

50 

32 

50 

32 

47 

38 

46 

34 

50 

32 

47 

43 

50+ 

38 

50+ 

41 

46 

18 

35 

35 

50 

41 

55 

Specific 
gravity. 


Chase  

Concord   

El   Monte   

Eureka    

Franquette   _— 

Mayette* 

Neff  

Placentia   

Prolific    

San  Jose  

A.    Bijou 

Seedling  No.   1. 
Seedling  No.   2. 


1.5  byl. 
1.45  by  1. 
1.7  byl. 
1.75  byl. 
1.75  byl. 

1.6  byl. 

1.7  byl. 

1.6  byl. 

1.7  byl. 
1.75  byl. 
2.25  byl. 
1.5  byl. 
1.5  byl. 


2   by  1.35 

2  by  1.3 
4  by  1.4 
25  by  1.3 
25  by  1.3 
25  by  1.25 

3  by  1.4 

2  by  1.3 

3  by  1.35 

4  by  1.5 

5  by  2 

2  by  1.3 
2  by  1.3 


67.5 

57 

60 

44.5 

50 

72 

60 


"These  samples  may  have  been  a  little  heavier  than  the  average. 


In  the  above  table  a  very  careful  effort  has  been  made  to  present 
average  statistics  of  the  varieties  given.  The  reader  should  know,  how- 
ever, that  this  is  an  extremely  difficult  thing  to  do,  since  some  of  the 
varieties  mentioned  perform  differently  in  one  part  of  the  State  than 
in  another,  and,  furthermore,  nuts  of  the  same  variety  vary  widely  on 
trees  of  different  ages  and  under  various  conditions  in  the  same  locality. 
Again,  especially  in  regard  to  weight  and  specific  gravity,  walnuts 
vary  to  a  considerable  extent  from  year  to  year.  For  absolutely 
average  statistics,  sample  nuts  would  be  necessary  from  various  parts 
of  the  State  from  trees  of  various  ages  and  on  different  types  of  soil 
and  from  the  crops  of  several  different  seasons.  It  is  impossible  to 
obtain  such  samples  at  the  present  time  in  the  case  of  practically  all 
the  varieties  mentioned.  The  best  that  we  can  do  is  to  present  what 
in  our  judgment  and  as  a  result  of  our  experience  are  fair,  average 
figures  for  these  varieties.  We  have  endeavored  particularly  to  bring 
out  the  comparative  size  and  weight  of  the  different  varieties  and 
believe  that  the  figures  given  are  fair  and  representative  in  this  respect. 
The  figures  given  were  obtained  as  follows: 

Weight. — Average  weights  were  obtained  by  weighing  large  num- 
bers of  nuts,  especially  in  the  case  of  the  more  prominent  varieties,  and 
averaging  these.  In  most  cases  nuts  of  more  than  one  season's  crop 
were  included.  Many  weighings  were  also  made  by  picking  out  indi- 
vidual nuts  of  average  size  and  weighing  these. 

Volume. — The  volume  was  obtained  by  partly  filling  a  graduated 
cylinder  with  water,  then  immersing  a  given  number  of  nuts  and  not- 
ing the  height  to  which  the  column  of  water  rose  in  the  cylinder.  The 
increase  was  then  divided  by  the  number  of  nuts,  giving  the  average 
volume  per  nut  in  cubic  centimeters.     Here,  again,  large  numbers  of 


Bulletin   231]  WALNUT   CULTURE   IN   CALIFORNIA.  301 

nuts  were  measured  in  some  cases  and  the  results  then  averaged,  while 
again  an  effort  was  made  to  pick  out  single  nuts  of  average  size  and 
these  were  measured  by  the  same  method.  It  should  be  clearly  under- 
stood in  regard  both  to  weight  and  volume  that  many  nuts  of  the  varie- 
ties mentioned  are  larger  than  these  figures  indicate  and  others  are 
smaller.  The  figures  are  intended  to  represent  the  average  size  which 
the  grower  may  expect  to  obtain  from  trees  of  these  varieties  over  a 
series  of  years.  It  will  be  noted  that  size  and  weight  are  not  always 
proportionate.  San  Jose,  for  instance,  is  about  the  same  weight  as 
Concord,  but  nearly  50  per  cent  larger. 

Dimensions. — The  dimensions  were  obtained  by  picking  out  nuts  of 
average  size  and  measuring  the  length  of  their  three  axes,  first  longi- 
tudinally, second  through  the  shorter  diameter  and  third  at  right  angles 
to  the  last  through  the  longer  diameter. 

N 'umber  per  Pound. — This  figure  is  intended  to  represent  the  aver- 
age number  of  nuts  per  pound,  as  they  would  average  in  large  quan- 
tities and  without  grading  as  to  size. 

Percentage  Meat. — This  figure  represents  the  percentage  of  meat  in 
the  total  weight  of  the  nut.  For  instance,  in  the  first  variety  given, 
Chase,  there  would  be  47  pounds  of  meat  and  53  pounds  of  shell  in  100 
pounds  of  nuts.  The  percentage  of  meat  varies  somewhat  according  to 
the  degree  of  dryness  of  the  nut.  It  is,  therefore,  impossible  to  give 
definite  figures  in  this  respect  without  some  standard  as  to  the  dryness  or 
moisture  content.  Nuts  of  the  same  variety  may  vary  nearly  10  per 
cent  in  the  amount  of  meat,  according  to  the  age  and  moisture  content 
of  the  samples.  After  the  first  drying  out  of  the  nuts,  however,  fol- 
lowing the  harvest  season  and  before  they  have  become  extremely  dry, 
that  is  during  the  period  from  about  December  15th  to  March  1st  fol- 
lowing the  gathering  of  the  nuts,  they  have  a  fairly  constant  weight 
when  kept  constantly  dry  at  room  temperature.  This  is  the  basis  upon 
which  the  figures  given  are  calculated.  In  each  of  the  varieties  given 
the  percentage  of  meat  sometimes  runs  higher  and  sometimes  lower 
than  the  figures  given,  but  these  represent  as  nearly  as  possible  aver- 
age figures  and  we  believe  them  to  be  accurate  on  a  comparative  basis 
between  one  variety  and  another.  In  weighing  the  meat  and  shell 
everything  except  the  meat  proper,  that  is  particularly  the  septa  or 
partitions  between  the  divisions  of  the  meat,  is  included  with  the  shell. 

It  will  be  noted  that  in  all  the  good  varieties  the  percentage  of  meat 
lies  between  45  and  a  little  over  50.  A  variety  which  .averages  less 
than  45  per  cent  of  meat  in  fairly  dry  nuts  can  hardly  be  considered 
worthy  of  consideration,  while  one  which  runs  over  50  per  cent  is 
exceptional.     The  comparative  percentage  of  meat  in  various  varieties 


302  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


Fig.   74. — Neff  walnut,  natural  size. 


Bulletin   231]  WALNUT    CULTURE    IN    CALIFORNIA.  303 

is  influenced  largely  by  the  actual  weight  of  the  meat  and  shell;  some 
varieties  have  a  good  meat,  but  also  a  heavy  shell,  while  others  may 
have  no  more  or  even  less  meat  per  nut,  but  a  rather  lighter  shell,  giv- 
ing a  higher  percentage  to  a  variety  with  less  meat.  Eureka  and  Neff, 
for  instance,  have  47  per  cent  meat  against  50  per  cent  or  more  in 
Placentia.  The  two  former  varieties,  however,  average  only  32  nuts  to 
the  pound,  while  with  Placentia  it  takes  an  average  of  43  to  make  a 
pound.  In  other  words,  in  one  average  Eureka  nut  there  is  about  7 
grams  of  meat,  while  in  a  Placentia  nut  there  is  only  5.4  grams, 
although  the  two  nuts  are  of  nearly  equal  size.  Varieties  like  Eureka, 
Neff  and  El  Monte  have  heavy  shells,  as  well  as  heavy  meats,  and  the 
same  is  true  to  a  considerable  extent  with  Chase,  Franquette  and  Pro- 
lific. This  condition  is  indicated  by  the  high  specific  gravity  of  these 
varieties. 

An  instructive  comparison  is  afforded  by  the  figures  given  at  the 
end  of  the  table  for  Seedlings  No.  1  and  No.  2.  These  nuts  average 
exactly  the  same  size,  both  in  volume  and  dimensions,  but  No.  1  is 
considerably  heavier  than  No.  2,  the  number  of  nuts  per  pound  being 
respectively  35  and  41.  No.  1  is  a  nut  of  exceptional  weight  both  of 
meat  and  shell,  being  of  only  medium  size,  yet  one  of  the  heaviest 
varieties  in  the  list  and  at  the  same  time  having  50  per  cent  meat.  Its 
specific  gravity,  72,  is  the  highest  of  any  nut  which  we  have  tested,  yet 
it  is  a  soft  shell  and  easily  cracked  in  the  fingers,  though  well  sealed. 
Seedling  No.  2,  of  the  same  size  but  lighter  weight  than  No.  1,  is  a  nut 
of  exceptionally  heavy  meat  (  55  per  cent)  and  very  light,  weak  shell. 
On  the  latter  account  it  is  probably  worthless,  commercially,  although 
of  such  exceptionally  good  meat. 

Specific  Gravity. — This  figure  is  obtained  by  dividing  the  weight  in 
grams  by  the  volume  in  cubic  centimeters.  This  represents  the  com- 
parative weight  of  nuts  of  the  same  volume  or  size  in  the  different  vari- 
eties. For  instance,  with  Chase  and  Placentia,  which  are  practically 
of  the  same  size,  the  weight  of  sacks  of  nuts  of  equal  size  would  be  as 
63  to  57  in  favor  of  Chase,  while  the  number  of  nuts  would  be  the  same. 
Chase  and  Concord  having  the  same  specific  gravity,  63,  would  weigh 
alike  in  sacks  of  the  same  size,  but  it  would  take  more  Concord  than 
Chase  nuts  to  fill  the  sack  in  the  proportion  of  19  to  17.5.  Comparing 
the  Eureka  and  San  Jose,  sacks  of  equal  size  would  weigh  66  pounds 
of  Eureka  to  every  44.5  pounds  of  San  Jose,  while  at  the  same  time 
there  would  be  more  Eureka  nuts  in  the  sack  in  the  proportion  of  25 
to  22.  Comparing  Eureka  with  Franquette,  the  weights  of  sacks  of 
equal  size  would  be  as  66  to  60,  with  the  size  of  the  nuts  and,  there- 
fore, the  number  of  nuts  per  sack  about  the  same.  The  most  desirable 
qualities  are  high  specific  gravity,  fairly  large  size,  small  number  per 
pound  and  high  percentage  of  meat. 


304 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


Fig.   75. — El  Monte  walnuts,  natural  size. 


Bulletin   231]  WALNUT   CULTURE   IN    CALIFORNIA.  305 


MISCELLANEOUS  AND  LESS  PROMINENT  VARIETIES. 

The  following  is  intended  to  complete  as  fully  as  possible  a  list  and 
description  of  all  the  walnut  varieties  of  any  importance  in  California. 
Many  of  them  are  old  French  varieties  which  have  not  proven  worthy 
of  extensive  commercial  planting.  Others  are  varieties  not  yet  fully 
tested  and  most  of  the  remainder  have  been  discarded  or  never  become 
prominent  for  various  reasons.  Bearing  trees  of  most  of  the  varieties 
in  this  list  which  are  of  any  importance  may  be  found  in  the  State. 
At  the  California  Nursery  Company,  Niles,  there  is  a  collection  of  most 
of  the  French  and  some  other  varieties ;  S.  F.  and  F.  A.  Leib,  of  San 
Jose,  have  a  large  miscellaneous  collection;  Mr.  Ely  Hutchinson,  of 
Concord,  has  a  great  many  in  bearing ;  Dr.  W.  W.  Fitzgerald,  of  Stock- 
ton, has  younger  trees  of  many  different  kinds,  and  there  are  various 
other  places  in  the  north  where,  collectively,  authentic  specimens  may 
be  found  of  bearing  trees  of  almost  all  the  varieties  which  we  mention. 
In  the  San  Joaquin  Valley  the  Fancher  Creek  Nursery  Company  has 
bearing  trees  of  a  number  of  varieties.  In  the  south  there  are  several 
of  the  French  varieties  on  the  old  Experiment  Station  grounds  near 
Pomona,  and  our  Whittier  Laboratory  has  a  collection  of  practically 
every  important  variety  growing  either  at  Whittier  or  on  the  Pasadena 
City  farm  near  Alhambra. 

ACME. 

Introduced  by  F.  C.  "Willson,  of  Sunnyvale,  California,  in  1910.  An 
extra  large  nut  of  Bijou  origin.  The  nut  is  fairly  smooth,  rather  elon- 
gated, larger  at  the  apex  than  at  the  base  and  almost  square  in  end 
view.  The  shell  is  quite  heavy  and  fairly  well  filled  with  meat,  which 
forms  less  than  40  per  cent  of  the  total  weight.  The  variety  is  not 
apparently  of  any  special  value  for  general  commercial  purposes. 

BARTHERA. 

Introduced  from  France  by  Felix  Gillet  in  1871.  Of  no  apparent 
value  in  California. 

A  BIJOU   (Gant). 

A  French  variety,  noteworthy  for  the  extremely  large  size  of  the 
nuts.  Nuts  very  rough  and  poorly  filled  with  meat  and  of  no  commercial 
value,  save  as  a  curiosity.  Bearing  trees  are  quite  abundant  in  the 
State.  Numerous  Bijou  seedlings  are  to  be  found  in  California,  many 
of  which  have  much  smoother  and  better  nuts  than  those  of  the  parent. 
See  "Acme,"  "Klondyke,"  and  " Wonder.' ' 

13—231 


306 


UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION. 


Fig.  76. — Various  walnut  varieties.     A,  Meylan  ;  B,  Mayette  ;  C,  Hale  ;  D,  Kaghazi 
E,  Seedling  501  ;  F,  Acme  ;  G,  Bijou.     Natural  size. 


Bulletin   231]  WALNUT   CULTURE  IN   CALIFORNIA.  307 

BISHOP. 

We  designate  by  this  name  a  tree  of  some  local  fame,  which  stands 
on  the  Bishop,  formerly  the  Colonel  Hollister  and  still  earlier  the  Denn 
Ranch,  north  of  Goleta  in  Santa  Barbara  County.  This  tree  is  upwards 
of  forty  years  old,  and  is  the  one  remaining  survivor  of  a  former  plant- 
ing, now  surrounded  by  a  young  orchard  composed  of  its  own  seedlings. 
The  tree  is  said  to  have  been  grown  from  a  French  nut  and  is  called 
locally  a  Grenoble  tree.  It  is  a  large,  heavy-bearing  tree,  coming  out 
decidedly  late  in  the  spring  and  practically  free  from  blight.  The  nuts 
are  not  particularly  attractive,  though  of  average  quality.  The  tree 
is  not  extremely  late,  but  would  probably  come  out  about  with  Con- 
cord and  Eureka  if  grown  in  the  same  locality.  We  doubt  whether  the 
nut  is  good  enough  to  make  the  propagation  of  this  tree  desirable  as  a 
special  variety,  by  grafting,  although  its  good  bearing  qualities  and 
freedom  from  blight  are  valuable  characteristics.  Many  nuts  from  this 
tree  have  been  planted  by  Mr.  Robert  Main,  superintendent  of  the 
ranch,  and  in  this  way  a  local  seedling  strain  has  been  developed,  called 
the  Main  nut.  There  is  a  large  orchard  of  these  seedlings  on  the  Bishop 
place  surrounding  the  old  tree,  Mr.  Main  has  a  number  of  acres  of 
them  on  his  home  place  at  Goleta,  and  there  are  others  scattered  about 
the  neighborhood.  Many  of  these  are  now  old  enough  to  bear  consid- 
erable crops.  It  is  remarkable  that  the  seedlings  of  this  comparatively 
late  and  blight-free  tree  have  proved  almost  without  exception  to  be 
early  in  coming  out  and  particularly  susceptible  to  blight.  The  tree 
has  apparently  been  crossed  by  the  surrounding  Santa  Barbara  Soft 
Shell  seedlings,  or  in  any  event  almost  all  of  its  own  seedlings  come  out 
decidedly  early  in  the  spring  and  blight  very  badly.  Only  one  of  the 
seedlings  of  this  tree  has  yet  been  found  which  shows  any  promise  of 
freedom  from  blight.  This  is  the  so-called  Hicks  tree,  growing  on  Mr. 
William  Hicks'  place,  between  Santa  Barbara  and  Goleta.  This  par- 
ticular tree  comes  out  early  in  the  spring,  but  has  thus  far  been  quite 
free  from  blight,  although  surrounded  by  badly  affected  trees.  It  bears 
a  nut  of  rather  rough  shape,  but  well  filled,  well  sealed,  light  colored 
meat,  good  size  and  excellent  flavor. 

There  is  reason  to  hope  that  among  the  seedlings  of  the  old  Bishop 
tree  there  may  yet  be  found  some  particularly  good  and  blight-free 
individuals. 

CHABERTE. 

An  old  French  variety  which  was  introduced  into  California  by 
Felix  Gillet  and  considerably  planted  in  the  central  and  northern  part 
of  the  State  some  years  ago.  The  tree  is  a  good  producer  of  small  nuts 
with  plump,  light  colored  meat.  Not  worthy  of  commercial  planting 
in  California. 


308 


UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 


CLUSTER. 

One  of  Felix  Gillet's  varieties,  introduced  by  him  from  France,  and 
so  named  on  account  of  the  habit  of  producing  nuts  in  large  clusters. 
Not  commercially  important. 

EL  MONTE  (El  Monte  Large). 

A  Santa  Barbara  Soft  Shell  seedling  from  the  vicinity  of  El  Monte, 
which  has   been  propagated  locally   in   southern   California   to   some 


Fig.   77. — Willson  walnut,  showing  young  tree  next  year  after  transplanting. 


extent.  The  variety  appears  to  be  worthy  of  some  little  consideration 
although  we  have  not  much  definite  information  concerning  it.  It  is  a 
large,  quite  rough,  somewhat  irregularly  shaped  nut,  with  pronounced 
sutural  ridges  and  a  decided  beak  or  short,  sharp  point  at  the  apex.  The 
nuts  are  well  sealed  and  filled  with  fairly  light  colored  meat  of  pleasant 
flavor.     The  tree  is  a  decidedly  precocious  bearer  and  thrifty  grower. 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  309 

It  is  early  in  foliation  and  harvest  period,  with  probably  no  particular 
blight  resistance,  although  definite  information  is  lacking  on  this  point. 
The  large,  well-filled  nut  and  precocious  bearing  of  the  tree  make  this 
variety  rather  promising. 

EUREKA  No.  2. 

Another  of  the  Stone  Kaghazi  seedlings,  standing  just  west  of  the 
original  Eureka  tree.  Mr.  Ware  has  six-year-old  trees  of  this.  It 
is  a  large,  full-meated  nut,  a  little  rougher,  softer-shelled  and  darker- 
meated  than  the  Eureka. 

FORD'S   IMPROVED. 

A  selection  from  the  Santa  Barbara  Soft  Shell  introduced  by  G.  W. 
Ford,  of  Santa  Ana.  This  variety  appears  to  have  been  propagated 
largely  by  seedlings,  and  has  now  become  almost  lost,  or  at  any  rate 
it  is  no  longer  planted  or  propagated  under  the  above  name. 

FORD'S  EUREKA. 

A  Santa  Barbara  Soft  Shell  selection.     Obsolete. 

GRENOBLE. 

A  general  name  applied  in  California  to  walnuts  of  French  origin. 
The  name  is  supposed  to  indicate  the  Mayette  type  to  some  extent. 

HALE. 

A  variety  named  and  propagated  to  some  extent  by  the  Experiment 
Station,  originating  in  a  seedling  tree  in  the  orchard  of  Mr.  William 
Hale,  between  Fullerton  and  Placentia.  The  variety  was  first  men- 
tioned by  name  in  Bulletin  203  of  the  California  Experiment  Station, 
where  it  is  figured  on  page  25.  In  this  orchard  there  was  formerly 
a  considerable  block  of  seedlings  of  some  French  variety,  the  trees  of 
which  varied  widely  in  size,  foliation  period  and  character  of  the  nuts. 
Among  these  one  particular  tree  was  selected  as  being  of  some  promise 
for  commercial  planting.  This  tree  was  medium  late  in  coming  out, 
free  from  blight,  large  and  thrifty,  and  a  fairly  heavy  producer.  A 
considerable  amount  of  top-grafting  with  this  variety  was  done  on 
orchard  trees  in  Los  Angeles  and  Orange  counties  about  1907  and 
1908.  When  thus  propagated  the  variety  proved  to  be  fairly  quick 
in  coming  into  bearing,  but  of  rather  slow  growth,  making  very  stocky 
branches  with  considerable  tendency  toward  the  production  of  fruiting 
wood,  but  of  rather  short  annual  growth  in  length.  The  variety,  like 
all  others  with  a  late  foliation  period  in  the  spring,  has  not  fully 
established  its  value  in  the  south,  but  it  may  yet  become  of  commercial 
importance  in  some  portions  of  the  State.     The  original  tree,  together 


310  UNIVERSITY   OF    CALIFORNIA EXPERIMENT   STATION. 

with  the  whole  grove  in  which  it  stood,  was  cut  down  in  1911  to  make 
way  for  oranges.  The  nut  is  medium  large,  decidedly  elongated,  with 
the  apex  as  broad  as  the  base.  Considerably  like  Franquette  (of  which 
it  may  be  a  seedling)  in  form  and  size,  but  broader  and  less  pointed 
at  the  apex.  The  nuts  are  strongly  sealed  but  easily  cracked,  with  a 
light-colored  meat  which  is  usually  plump  and  well  filled,  with  a  par- 
ticularly sweet  and  agreeable  flavor.  This  is  the  sweetest  nut  of  any 
variety  which  we  have  tested. 

The  value  of  this  variety  for  commercial  planting  has  not  been  thor- 
oughly established,  and  we  do  not  wish  to  recommend  it  for  such 
purposes  at  present.  It  is  possible,  however,  that  it  may  prove  worthy, 
especially  in  the  north.  The  nut  is  quite  similar  to  that  of  the  Fran- 
quette, but  slightly  inferior  to  it  in  some  respects.  Judging  from  the 
original  tree,  however,  it  may  prove  a  heavier  and  more  precocious 
bearer  than  the  Franquette.  It  is  late  enough  in  the  spring  to  escape 
frost,  decidedly  free  from  blight  and  not  objectionably  late  in  the  fall. 
Its  foliation  and  harvest  season  is  much  the  same  as  that  of  Concord 
and  Eureka.  We  recommend  this  variety  for  limited  trial,  more  par- 
ticularly in  the  north. 

HICKS  (see  Bishop). 

HILDEBRAND   (see  Mayette). 

KAGHAZI. 

This  is  a  name  occasionally  heard  in  California  in  connection  with 
walnut  varieties  and  is  supposed  to  denote  a  variety  native  to  Persia. 
In  an  article  quoted  from  the  Gardners'  Chronicle  in  the  Rural  Cali- 
fornian,  No.  9,  Vol.  19,  September,  1896,  we  find  the  following  state- 
ment :  ' '  The  Persian  walnut  is  about  a  third  or  a  half  larger  than  the 
English  walnut ;  of  an  elongated  shape,  with  a  very  rich  meat  or  kernel 
and  a  shell  as  thin  as  paper.  It  is  not  an  unusual  thing  for  a  tree 
eight  to  twelve  years  old  to  bear  30,000  nuts  or  1200  pounds. ' '  *  *  * 
"There  are  four  kinds,  the  Kanate,  the  Wanter,  the  Denu  and  the 
Kaghazi,  the  last  of  which  is  the  finest  nut  grown. ' ' 

In  Fuller's  "Nut  Culturist"  we  find  the  following:  "Kaghazi.— This 
is  supposed  to  be  a  variety  of  the  Persian  walnut  of  fair  size  with  a 
very  thin  shell.  The  tree  blooms  very  late  in  the  spring,  and  for  this 
reason  is  recommended  for  localities  where  there  is  danger  from  injuries 
by  frost.  The  tree  is  said  to  be  a  very  rapid  grower  and  much  more 
hardy  than  the  general  run  of  varieties  of  this  species.  We  have  been 
unable  to  learn  its  origin,  but  it  has  been  planted  to  quite  an  extent  in 
California  and  some  of  our  eastern  nurserymen  are  offering  the  seedling 
trees  for  sale,  but  whether  they  will  possess  the  merits  of  the  original 
or  not  must  be  determined  by  experience." 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  311 

In  Wickson's  "California  Fruits,"  we  find  the  following:  "Kaghazi: 
A  variety  called  Kaghazi  was  grown  and  propagated  for  several  years 
by  the  late  James  Shinn  of  Niles,  who  described  it  is  follows:  'very 
much  larger  than  the  ordinary  kinds  and  thinner  shelled.  The  tree  is 
late  in  putting  out  leaves  and  blossoms,  and  is  therefore  especially  good 
for  places  that  are  in  danger  of  late  frosts.'  " 

It  appears  from  the  above  quotations  that  the  Kaghazi  is  an  extra 
large,  elongated,  extremely  thin-shelled  nut,  borne  on  a  tree  which 
comes  out  late  in  the  spring.  The  variety  would  have  no  particular 
importance  in  California  at  the  present  time  were  it  not  for  its  apparent 
relation  to  the  Eureka,  the  parent  tree  of  which  resembles  very  closely 
the  above  description  of  the  Kaghazi.  We  have  mentioned  in  describing 
the  Eureka  the  fact  that  the  original  tree  at  Fullerton  was  found  to 
be  a  seedling  from  a  still  older  tree  standing  on  the  Meek  homestead 
near  Hay  wards.  The  particular  tree  which  is  the  mother  of  the  Eureka 
is  the  southernmost  one  of  two  which  stand  just  east  of  the  Meek  resi- 
dence. This  old  tree  bears  an  unusually  large,  long,  extremely  thin- 
shelled  nut,  coinciding  exactly  with  the  description  of  the  Kaghazi. 
In  regard  to  the  origin  of  this  tree,  Mr.  H.  W.  Meek,  now  deceased, 
made  the  following  statement :  ' '  All  I  know  about  these  trees  is  that  a 
neighbor  of  my  father's  gave  him  a  few  walnuts  a  number  of  years  ago 
which  he  claimed  he  had  received  from  the  United  States  representative 
in  Persia.  My  father  planted  the  nuts,  and  the  two  trees  which  I  have 
at  present  are  the  result.  I  do  not  know  whether  the  walnut  propa- 
gated by  the  late  James  Shinn  has  anything  to  do  with  the  trees  or 
variety  which  I  have  growing  here.  The  Stones  of  Fullerton  have  some 
trees  growing  from  the  nuts  from  my  trees  here,  but  I  have  never  heard 
how  they  turned  out."  In  regard  to  the  Shinn  trees,  Mr.  J.  C.  Shinn 
states  as  follows:  "The  Persian  walnuts  we  have  possibly  came  from 
the  same  party  referred  to  in  a  letter  from  Mr.  Rixford  which  I  enclose, 
though  my  memory  is  that  they  came  from  some  one  in  Illinois  who  had 
tried  trees  raised  from  nuts  direct  from  Persia  and  found  them  too 
tender.  They  were  bought  about  the  year  mentioned  by  Mr.  Rixford. 
The  late  James  Shinn  bought,  as  he  understood,  the  whole  stock  of  the 
party  who  brought  the  nuts  over.  The  party  sent  a  few  nuts  as  a 
sample  and  they  were  a  very  large,  thin-shelled  nut.  There  had  been 
some  report  in  a  United  States  agricultural  report  about  that  time  that 
had  aroused  his  interest.  "We  sold  many  seedling  trees,  much  seed  for 
planting,  and  later  quite  a  number  of  grafted  trees  of  the  Persian  or 
Kaghazi  walnut.  There  must  be  thousands  of  bearing  trees  in  the  State 
from  those  we  sold."  The  letter  from  Mr.  Rixford,  referred  to,  states 
as  follows :  "In  September,  1873,  Mr.  Finch  of  Alameda  ordered  from 
Rosse  &  Grant,  Topeka,  Kansas,  fifty  Persian  or  Kaghazi  walnut  trees. 


312  UNIVERSITY   OF   CALIFORNIA — EXPERIMENT   STATION. 

The  stock  being  short,  he  secured  but  thirty-six.  Of  these  he  sold  to 
Mr.  Latham  ten  at  ten  dollars  each,  to  Mr.  Selby  two,  to  J.  D.  Roberts 
four,  and  to  Mr.  Meek  of  Alameda  twelve.  Rosse  &  Grant  claim  to  have 
obtained  the  seed  from  the  Cashmere  Valley,  Persia. ' ,#  Further  inquiry 
of  Mr.  Shinn  in  regard  to  the  parties  mentioned  in  this  letter  brought 
out  further  information  in  regard  to  the  extensive  scale  upon  which 
Kaghazi  trees,  mostly  seedlings,  were  sold  by  his  father  during  the 
eighties  and  nineties. 

It  is  evident  from  what  we  have  said  that  this  is  a  fairly  distinct 
variety,  and  that,  if  Mr.  H.  W.  Meek's  memory  was  correct,  it  was 
introduced  independently  into  California  by  his  father,  "William  Meek, 
and  the  late  James  Shinn.  Trees  are  still  to  be  found  here  and  there 
about  the  State  which  are  evidently  of  this  sort.  There  are  several  long 
rows  of  the  seedlings  on  the  old  Meek  place,  some  extending  from  the 
residence  toward  the  town  of  Hay  wards  and  others  along  various  other 
roads.  There  are  a  number  of  trees  of  similar  nature  in  Contra  Costa, 
and  in  that  locality  one  particular  type  of  this  sort  has  been  quite 
extensively  propagated  by  grafting  under  the  name  of  Persian.  A  large 
number  of  the  older,  top-grafted  walnut  trees  in  the  San  Ramon  and 
other  valleys  in  the  Mount  Diablo  country  are  of  this  so-called  Persian 
variety.  There  is  quite  a  number  of  trees  of  Kaghazi  type  in  the 
vicinity  of  the  Shinn  place  at  Niles  and  also  about  the  Niles  High  School 
and  vicinity.  Near  Goleta  there  is  a  considerable  orchard  of  similar 
seedlings  on  the  ranch  of  the  Goleta  Walnut  Company.  These  trees 
vary  quite  widely  in  many  respects,  but  as  a  whole  they  are  marked  by  a 
late  and  irregular  coming  out  in  the  spring  and  the  peculiar  appearance 
of  the  bark  on  the  trunk,  which  is  cracked  or  grooved  characteristically 
in  an  up  and  down  direction.  A  great  many  of  the  trees  bear  nuts 
which  are  extremely  thin-shelled  and  poorly  sealed,  and  some  of  them 
are  quite  desirable  except  for  this  defect.  Some  of  them  are  nuts  of  the 
highest  eating  quality,  of  fine  shape  and  beautiful,  light-colored  shell 
and  meat,  but  with  shells  which  open  at  the  slightest  pressure  of  the 
fingers.  It  is  remarkable  that  of  the  many  hundreds  and  thousands  of 
seedlings  of  the  Kaghazi  type  which  have  been  brought  into  bearing  in 
California  only  one,  the  Eureka,  has  shown  exceptional  worth.  It  seems 
probable  that  this  is  the  result  of  a  cross  of  the  original  Meek  Kaghazi 
tree  with  some  hard-shelled  English  walnut  in  the  vicinity,  as  the  shell 
of  the  Eureka  is  particularly  hard,  strong,  and  well  sealed. 


*The  Kashmir  Valley  lies  just  northwest  of  India  rather  than  in  Persia,   and  is, 
we  are  credibly  informed,  the  home  of  the  Kaghazi  walnut. 


Bulletin   231]  WALNUT   CULTURE   IN   CALIFORNIA.  313 

KEESLING. 

A  rather  promising  walnut  has  recently  been  sent  us  by  Mr.  H.  G. 
Keesling,  of  San  Jose.  This  is  the  variety  called  Seedling  No.  2  in  the 
table  on  page  300.  The  nut  is  particularly  well  filled,  of  good  quality, 
and  has  the  highest  specific  gravity  of  any  which  we  have  mentioned. 
We  know  nothing  of  the  bearing  quality  or  other  characteristics  of  the 

tree. 

KLONDYKE. 

A  name  applied  in  southern  California  to  very  large  walnuts  of  the 
Bijou  type.  The  name  seems  first  to  have  been  given  to  a  particular 
tree  of  this  sort  in  the  vicinity  of  Santa  Ana. 

LACINIATED. 

A  variety  introduced  by  Felix  Gillet,  having  finely  cut  or  divided 
leaves,  giving  an  ornamental  effect.  Not  commercially  important, 
although  the  tree  is  a  good  bearer  of  very  good  nuts.  The  tree  is 
decidedly  ornamental  on  account  of  its  graceful  foliage.  Specimen 
tree  at  California  Nursery  Company,  Niles. 

LANE. 

This  is  a  local  Santa  Barbara  variety  which  has  been  propagated  by 
grafting  to  a  slight  extent  in  that  vicinity.  The  variety  receives  its 
name  from  Mr.  Miles  P.  Lane  who  has  a  young  grafted  tree,  the  scions 
having  been  obtained  from  Mr.  W.  H.  Johnson,  on  whose  ranch  the 
original  tree  is  growing.  The  latter  is  a  Santa  Barbara  County  seedling 
of  unknown  parentage.  The  variety  is  decidedly  early  in  coming  out 
in  the  spring,  but  yet,  as  thus  far  shown,  it  is  entirely  free  from  blight, 
although  immediately  surrounded  by  badly  blighted  trees  in  the  same 
orchard.  The  nut  is  of  light  color  and  heavy,  well  flavored,  light  colored 
meat.  The  tree  appears  to  be  a  prolific  and  precocious  bearer.  It  has 
much  promise  of  making  an  unusually  good  variety,  save  for  the  one 
fact  that  the  nuts  are  very  poorly  sealed,  breaking  open  at  the  slightest 
pressure.  For  this  reason  there  is  some  doubt  whether  this  can  be  con- 
sidered a  good  commercial  nut.  It  appears  to  have  real  resistance  to 
the  blight  organism,  inasmuch  as  the  trees  come  out  so  early  and  still 
are  free  from  the  disease,  though  abundantly  exposed.  This  variety  is 
the  Seedling  No.  1  mentioned  in  the  table  on  page  300. 

MAIN    (see  Bishop). 
MAYETTE. 

This  is  an  old  French  variety  and  is  considered  the  choicest  of  the 
French  kinds. 

The  Mayette  in  California  varies  quite  widely  in  character  and  leads 
one  to  suppose  that  either  there  has  been  considerable  mixing  in  the 


314  UNIVERSITY   OP   CALIFORNIA — EXPERIMENT   STATION. 

introduction  of  this  variety  or  else  the  Mayette  in  France  represents  a 
general  type  propagated  largely  by  seedlings,  like  our  Santa  Barbara 
Soft  Shell,  rather  than  a  distinct  variety  propagated  exclusively  by  bud- 
ding or  grafting.  Most  of  the  so-called  Mayettes  in  California  have  a 
general  resemblance  to  one  another  and  appear  to  be  seedlings  or  deriva- 
tives of  the  same  general  type. 

The  variety  is  characterized  by  the  shape  of  the  nut.  In  the  true 
Mayette  type  the  base  of  the  nut  is  decidedly  flat  and  square-cut,  so  that 
the  nut  can  easily  be  set  upon  the  basal  end  without  falling  over.  The 
nut  rounds  broadly  to  a  point  at  the  other  end,  giving  it  a  sort  of  flat- 
iron  shape.  In  good  Mayettes  the  meat  is  plump  and  well  developed, 
averaging  close  to  50  per  cent  of  the  total  weight,  and  very  light  colored 
and  attractive.  In  flavor  there  is  considerable  variation  in  various 
Mayette  types  found  in  this  State,  but  the  best  of  these  are  excellent  in 
this  respect.  The  shell  is  thin  but  strong  and  well  sealed.  The  Mayette 
is  a  tree  of  comparatively  late  coming-out  in  the  spring,  though  usually 
somewhat  earlier  than  the  Franquette.  It  is  decidedly  later  than  the 
southern  California  seedling  trees.  In  most  cases  the  time  of  maturity 
in  the  fall  is  fairly  early  as  compared  with  late  varieties,  though  some- 
what later  than  ordinary  California  seedlings.  Of  the  so-called  Mayettes 
to  be  found  in  California  some  have  no  resemblance  whatever  to  this 
variety  and  need  not  be  considered.  Among  those  which  have  the  true 
flatiron  shape  Mayette  type  of  nut,  with  a  flat  base  upon  which  the 
nut  can  easily  be  set  up,  there  is  still  considerable  variation.  Of  the 
older  trees  which  are  attributed  to  Felix  Gillet,  many  are  evidently 
seedlings  and  thus  vary  to  a  greater  or  less  extent.  No  especially  desir- 
able true  Mayette  type  has  thus  far  appeared  among  the  older  Gillet 
trees.  Probably  the  best  Mayettes  in  the  State  are  to  be  found  on  S.  F. 
Leib's  place  at  San  Jose,  these  being  trees  grown  from  a  large  lot  of 
scions  which  Judge  Leib  imported  from  France  about  five  years  ago.  In 
this  importation  an  effort  was  made  to  obtain  the  best  type  of  the  true 
French  Mayette,  but  among  the  trees  grown  from  these  scions  wide 
variations  have  appeared.  Some  of  these  trees,  however,  represent, 
as  we  have  said,  what  appears  to  be  the  best  Mayette  type  in  the  State. 
These  are  large,  smooth,  light  colored,  attractive  looking  nuts  of  typical 
shape.  They  are  well  filled  with  very  light  colored  meat  of  excellent 
flavor.  The  growth  appears  to  be  more  vigorous  than  that  of  the  Fran- 
quette. It  is  not  improbable  that  had  a  Mayette  type  as  good  as  this 
been  introduced  and  planted  on  a  large  scale  a  number  of  years  ago,  it 
might  have  proved  as  good  or  even  better  than  the  Franquette.  Under 
existing  circumstances,  however,  it  is  not  possible  to  judge  the  variety 
critically  as  to  production  and  other  important  considerations.  Mr. 
Ely  Hutchinson,  at  Concord,  has  a  number  of  trees  of  a  Gillet  Mayette 


Bulletin    231]  WALNUT    CUL1URE   IN    CALIFORNIA.  315 

with  which  he  has  been  quite  well  satisfied  and  which  he  is  inclined  to 
put  ahead  of  the  Franquette  for  his  locality  at  least.  On  the  former 
Kerr  ranch  near  Elk  Grove,  now  belonging  to  a  Mr.  Powell,  there  is  a 
valuable  collection  of  fairly  old,  producing  walnut  trees  top-grafted  on 
California  blacks,  which  originated  from  scions  which  Mr.  Kerr  imported 
from  France  a  number  of  years  ago.  There  are  trees  here  of  the 
Parisienne,  Franquette  and  some  other  varieties,  and  also  a  considerable 
number  of  Mayettes  of  a  very  good  type.  This  Mayette  has  received 
more  or  less  prominence  through  Tribble  Brothers  of  Elk  Grove,  who 
have  propagated  it  to  a  considerable  extent.  There  is  some  variation 
between  the  various  Mayette  trees  on  the  place,  but  this  may  be  largely 
accounted  for  by  differences  in  soil  and  moisture  conditions  where  the 
various  trees  stand.  This  Tribble  Mayette  is  the  best  tested  of  any  in 
California,  and  appears  to  have  no  little  merit.  The  trees  are  growing 
in  a  region  with  a  very  hot,  sunny,  summer  climate,  and  various  speci- 
mens may  be  seen  about  Elk  Grove  which  are  growing  over  shallow 
hardpan  and  entirely  without  irrigation.  Nevertheless  the  nuts  are 
uniformly  white  meated,  with  no  discoloration  by  the  sun,  and  the  trees 
are  thrifty  growers  and  fairly  heavy  producers.  Another  tree,  appar- 
ently a  Mayette  seedling,  is  the  so-called  Hildebrand  tree  which  stands 
on  the  ranch  of  this  name  a  few  miles  above  Linden  and  not  far  below 
Milton  in  Calaveras  County  on  the  south  fork  of  the  Calaveras  River. 
It  is  said  that  this  tree  came  from  a  nut  distributed  by  Mr.  J.  P.  Rixf ord, 
then  of  the  San  Francisco  Bulletin,  in  1878.  In  an  article  in  the  Pacific 
Rural  Press  of  April  17,  1909,  the  suggestion  is  made  that  this  tree 
is  probably  of  the  Kaghazi  variety.  Such  is  probably  not  the  case, 
however,  as  the  character  of  the  nut  gives  every  reason  to  suppose  that 
the  tree  is  a  Mayette  seedling.  The  tree  is  unusually  large,  being  70 
feet  high  with  a  spread  of  about  60  feet,  and  is  in  a  perfectly  thrifty 
condition  with  no  sign  of  die-back  or  deterioration.  During  recent  years 
the  tree  is  said  to  have  produced  from  300  to  500  pounds  of  nuts  per 
year.  The  nut  is  of  fairly  good  Mayette  type,  but  not  of  exceptional 
quality.  It  is  possibly  of  some  promise  on  account  of  its  freedom  from 
sunburn,  as  the  tree  is  growing  in  a  very  hot  region.  It  is  also  unusually 
thrifty,  although  this  is  partly  accounted  for  by  the  fact  that  the  tree 
stands  alone  in  excellent  soil.  We  have  two  Mayette  trees  on  our  own 
grounds  which  were  imported  from  France  as  grafted  trees  by  Felix 
Gillet  in  1907.  These  trees  are  just  coming  into  bearing  and  have  pro- 
duced nuts  which  appear  to  be  of  an  excellent  Mayette  type. 

In  general,  then,  we  may  say  of  the  Mayette  that  it  is  very  much 
mixed  in  this  State,  and  outside  of  one  or  two  special  strains,  the  grower 
has  very  little  assurance  of  what  he  is  getting  in  buying  Mayette  trees. 
The  best  type  of  the  variety  is  represented  by  a  nut  of  very  high  quality, 


316  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

and  it  is  possible  that  such  a  Mayette  may  become  of  increased  impor- 
tance in  the  future  in  the  northern  part  of  the  State,  even  outranking 
the  Franquette.  It  does  not  appear  probable,  however,  that  any  of  our 
Mayettes  are  especially  heavy  bearers  in  the  south,  and  it  is  doubtful 
whether  any  variety  as  late  as  this  will  ever  become  of  great  importance 
or  value  there. 

MAYETTE  BLANC. 

This  name  is  supposed  to  indicate  the  true  Mayette. 

MAYETTE  ROUGE. 

A  variety  supposed  to  be  a  variation  of  the  Mayette,  with  a  reddish 
colored  shell.    Not  commercially  important. 

MESANGE. 

A  French  variety  described  as  bearing  a  nut  with  a  very  thin  shell. 
The  name  is  derived  from  a  little  lark  which  pecks  the  kernels  through 
the  thin,  tender  shell.    Not  important. 

MEYLAN. 

A  French  variety  having  the  reputation  of  being  the  finest  of  all 
walnuts.  The  nut  is  somewhat  of  the  Mayette  type,  having  a  broad, 
rather  flattened  base,  rounding  to  a  very  broad  point  at  the  other  end. 
The  surface  is  smooth,  having  a  light,  attractive  color.  Meat  very  light 
colored  and  fairly  well  filled.  Good  flavor.  This  variety  in  California 
is  probably  not  a  sufficiently  heavy  bearer  to  warrant  its  commercial 
planting,  although  the  nut  is  beautiful  in  appearance  and  of  high 
quality. 

MONSTREUSE. 

A  French  variety  of  which  there  is  a  tree  in  bearing  at  the  California 
Nursery  Company,  Niles.  Never  distributed  in  California  to  any  extent. 
The  nut  is  rather  large,  rounded,  with  smooth  surface  and  of  fine  appear- 
ance. Probably  not  commercial  in  California,  but  a  nut  of  exceptionally 
good  appearance. 

NEFF  (Neff's  Prolific.) 

A  tree  selected  from  his  orchard  for  propagation  by  Mr.  J.  B.  Neff, 
of  Anaheim.  The  original  tree  stands  in  Mr.  Neff's  old  orchard  and  is 
presumably  a  Santa  Barbara  Soft  Shell  seedling.  Mr.  Neff  selected 
this  tree  on  account  of  the  fact  that  it  was  averaging  about  200  pounds 
of  nuts  annually,  which  production  far  exceeded  that  of  any  other  tree 
in  its  vicinity.  Mr.  Neff  therefore  cut  back  many  of  his  poorest  pro- 
ducing trees  and  grafted  them  over  with  scions  from  this  heavy 
bearing  tree. 

The  original  tree  is  decidedly  free  from  blight,  although  not  totally 
immune  to  the  disease.     The  nut  is  of  good  size,  well  sealed,  excep- 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  317 

tionally  heavy  and  well  filled  with  light-colored  meat.  The  flavor  of  the 
nut  is  good.  In  form  the  nuts  are  rather  rough  and  irregularly  shaped, 
this  being  the  greatest  defect  of  an  otherwise  very  promising  variety. 
The  shell  is  heavy,  giving  the  nuts  good  weight  in  the  sack.  The  variety 
has  not  been  propagated  to  any  extent,  save  in  top-working  old  trees, 
so  nothing  can  be  said  as  to  its  behavior  as  a  young  tree.  For  a  heavy 
bearing,  heavy  weighing  variety  for  the  ordinary  commercial  trade,  the 
variety  has  considerable  promise.  For  a  fancy,  attractive  nut,  it  is 
not  so  good,  on  account  of  its  rough,  irregular  shape. 

PAPER  SHELL. 

This  is  a  general  name  applied  to  walnuts  with  exceptionally  thin 
shells.  The  name  is  also  applied  to  a  certain  type  of  tree  which 
originated  with  Joseph  Sexton,  of  Goleta,  along  with  the  original  trees 
of  the  Santa  Barbara  Soft  Shell  type.  These  paper  shells  were  so  called 
from  the  thinness  of  the  shell,  but  the  name  as  applied  in  the  Santa 
Barbara  section  refers  to  a  certain  type  of  tree,  some  of  which  have  real 
paper  shell  nuts,  while  others  do  not.  These  trees  are  of  a  characteristic 
small  size,  round  dense  top,  and  bear  a  small,  usually  roundish,  smooth, 
light  colored  nut.  Many  of  them  resemble  very  closely  the  Chaberte 
variety.  These  typical  paper  shell  trees  are  decidedly  susceptible  to 
blight,  and  on  account  of  this  quality  and  the  small  size  of  the  nuts  and 
trees  the  type  is  not  considered  desirable. 

PARISIENNE. 

A  French  variety  introduced  by  Gillet  and  others. 

This  is  one  of  the  best  of  the  French  varieties  and  might  become  com- 
mercially important  in  California  except  for  its  light  production.  The 
nut  is  rather  long  and  pointed,  somewhat  resembling  the  Franquette,  but 
broader  in  the  center.  The  shell  and  meat  are  both  light  colored;  the 
nut  fairly  well  filled  and  of  good  flavor.  Very  late  in  coming  out  in 
the  spring. 

PERSIAN   (see  Kaghazi). 

POWELL  (see  Mayette). 

PRIDE  OF  VENTURA. 

A  Santa  Barbara  Soft  Shell  seedling  tree  selected  by  E.  0.  Tucker 
of  Ventura,  California. 

This  is  said  to  be  a  very  precocious  and  heavy  bearer,  but  with  no 
special  immunity  to  blight.  The  nut  is  decidedly  large,  rather  round 
and  somewhat  rough.  This  variety  has  been  propagated  and  planted 
to  some  extent  in  the  vicinity  of  Ventura. 


318  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

PRCEPARTURIENS. 

A  French  variety  introduced  by  Gillet,  which  was  planted  quite  ex- 
tensively in  central  and  northern  California  some  years  ago.  The  nut 
is  rather  small  and  the  variety  can  no  longer  be  considered  worthy  of 
commercial  planting. 

SANTA  BARBARA  SOFT  SHELL. 

This  is  the  prevailing  type  of  seedling  walnut  of  southern  Cali- 
fornia, originated  by  Joseph  Sexton.  Its  history  has  been  described  at 
length  on  page  173.  The  trees  and  the  nuts  which  they  bear  vary 
to  a  considerable  extent  among  themselves,  but  yet  are  mostly  of  the 
same  general  type.  The  nuts  are  usually  of  good  size,  easily  cracked 
in  the  fingers,  and  of  excellent  flavor  and  quality.  The  trees  come  out 
fairly  early  in  the  spring  and  usually  produce  an  abundance  of  pollen. 
This  type  is  particularly  well  adapted  to  southern  California,  except  for 
its  susceptibility  to  walnut  blight  and  the  variation  in  trees  produced  by 
seedling  propagation  through  several  generations.  Some  of  the  varie- 
ties, like  Placentia  Perfection,  Discher's  Prolific,  Neff,  El  Monte,  Pride 
of  Ventura  and  others,  obtained  by  selecting  individual  trees  of  this 
type,  are  most  excellent  in  every  way  except  for  the  susceptibility  to 
blight  or  individual  minor  defects.  An  ideal  variety  may  yet  be  found 
among  the  many  hundreds  of  thousands  of  trees  of  this  type  now  grow- 
ing in  southern  California. 

SANTA   ROSA. 

A  variety  first  introduced  by  Luther  Burbank  and  considered  at  one 
time  of  great  promise  on  account  of  its  productiveness.  The  nut  is 
rather  small,  however,  and  has  proven  to  be  one  of  the  most  susceptible 
of  all  varieties  to  the  blight.  Consequently,  its  further  planting  cannot 
be  considered  advisable.  The  Payne  tree  at  San  Jose  is  top-worked 
with  this  variety  and  bears  immense  crops  of  nuts. 

SEEDLING  (see  Santa  Barbara  Soft  Shell). 
SEROTINA. 
A  French  variety  introduced  by  Gillet.    Of  no  commercial  importance. 

SOFT  SHELL   (see  Santa  Barbara  Soft  Shell). 
TREYVE. 

A  French  variety  of  the  Mayette  type  introduced  by  Gillet.  But 
very  little  planted  in  California.  This  is  a  beautiful  nut,  especially  on 
account  of  its  almost  pure  white  meat.  Mr.  Ely  Hutchinson,  of  Concord, 
has  the  variety  in  bearing.  Probably  not  commercially  important  on 
account  of  poor  production. 


Bulletin   231]  WALNUT   CULTURE   IN   CALIFORNIA.  319 

TRIBBLE   (see  Mayette). 
VOUREY. 

A  very  good  French  variety  introduced  by  Gillet,  but,  like  most  of  the 
other  French  varieties,  a  poor  producer  in  California. 

WAGNER. 

A  Royal  hybrid  tree  which  has  been  progagated,  advertised  and  sold 
by  Mr.  J.  B.  Wagner,  of  Pasadena.  The  tree  was  recommended  for 
shade,  wood,  and  timber.  The  original  appears  to  have  been  a  cross 
between  the  southern  California  black  walnut  and  an  eastern  or  pos- 
sibly Royal  black.     It  is  a  thrifty,  vigorous  type,  like  other  good  Royals. 

WILLSON   (Willson's  Wonder). 

A  Bijou  derivative  propagated  by  F.  C.  Willson,  of  Sunnyvale.  The 
nuts  are  very  large,  but  much  smoother  and  better  filled  than  those  of 
the  Bijou.  The  variety  is  claimed  to  be  extremely  immune  to  blight 
in  the  locality  of  its  origin.  It  is  also  particularly  claimed  for  the 
Willson  that  it  is  extremely  precocious,  bearing  nuts  while  still  in  the 
nursery  and  coming  immediately  into  bearing  after  planting  in  the 
orchard.  Figure  77  shows  a  young  tree  of  this  variety,  the  picture 
being  taken,  it  is  said,  the  next  year  after  the  tree  was  planted 
in  its  present  location.  The  variety  has  not  been  widely  enough  tested 
to  warrant  any  strong  statement  either  for  or  against  it.  Its  precocity 
in  bearing  appears  to  be  well  established,  and  being  quite  late  in  coming 
out  in  the  spring,  its  blight  immunity  may  be  counted  upon  to  a  con- 
siderable extent.  As  to  the  desirability  of  so  large  a  nut  as  this  for 
general  commercial  planting,  there  is  some  difference  of  opinion.  Some 
consider  the  nut  too  large  except  for  a  novelty;  Mr.  Willson  claims 
that  the  quality  of  the  nut  is  so  excellent  that  its  large  size  is  an  ad- 
vantage rather  than  otherwise.  It  may  certainly  be  said  that  the 
Willson  appears  to  be  much  the  best  of  any  of  these  extra  large  nuts. 
The  flavor  is  mild  and  sweet.  The  nut  is  decidedly  smooth  and  sym- 
metrical for  one  so  large,  being  somewhat  broader  at  the  apex  than 
at  the  base  and  nearly  square  in  end  view.  The  largest  nuts  on  some 
trees  measure  nearly  2  by  3  inches,  while  on  older  trees  an  average  size 
of  perhaps  1J  by  2  inches  may  be  expected. 

We  name  this  variety  "Willson"  rather  than  "Wonder"  with  the 
approval  of  the  originator. 


320  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT   STATION. 

DISEASES    AFFECTING    THE    WALNUT. 


WALNUT  BLIGHT   OR  BACTERIOSIS. 

This  is  by  far  the  most  important  trouble  affecting  the  walnut  in 
California.  So  serious  has  been  this  disease  that  the  loss  of  a  large 
portion  of  the  crop  has  in  some  years  been  charged  to  this  source; 
legislatures  have  made  special  appropriations  for  its  investigation,  and 
the  growers  have  offered  a  large  reward  for  a  practical  remedy.  The 
ravages  attributed  to  blight  were  the  occasion  of  the  investigations  de- 
scribed in  this  bulletin  and  the  prevalence  of  the  disease  has  resulted 
in  changing  the  whole  aspect  of  walnut  culture  in  California  within 
a  period  of  comparatively  few  years.  The  following  account  has  been 
prepared  mainly  by  Mr.  C.  0.  Smith,  who  has  carried  out  most  of  this 
portion  of  the  work. 

The  bacterial  diseases  of  plants  are  more  and  more  engaging  the  at- 
tention of  plant  pathologists.  Most  of  these  have  only  within  recent 
years  been  well  understood.  At  present,  however,  there  are  a  number 
of  very  definite  plant  troubles  due  directly  to  these  micro-organisms 
living  in  plant  tissues.  One  of  the  most  important  of  this  class  of 
plant  troubles  is  the  bacterial  blight  of  the  Persian  or  English  walnut. 

Bacterial  diseases  of  plants  are,  as  a  rule,  much  more  difficult  to  con- 
trol than  those  caused  by  fungi,  and  do  not  readily  yield  to  treatment 
by  spraying.  Our  experiments  in  spraying  will  be  described  in  full  at 
another  point  in  this  article,  but  the  unsatisfactory  results  we  secured 
in  checking  the  development  and  spread  of  the  disease  show  quite  con- 
clusively that  the  solution  of  this  problem  lies  along  other  lines. 
The  solution  of  the  trouble  is  quite  as  much  a  horticultural  as  a  phyto- 
pathological  problem,  involving  as  it  does  the  growing  of  varieties  that 
show  a  certain  amount  of  resistance  or  in  which  the  nuts  escape  the 
blight  because  of  their  late  period  of  blooming  in  the  spring  after  the 
period  of  blight  infection  is  largely  past.  The  walnut  industry  is 
just  now  in  a  state  of  transition  from  the  seedling  orchard  to  one  con- 
taining only  the  best  and  most  productive,  non-blighting  varieties.  A 
number  of  these  have  been  quite  thoroughly  studied  by  the  Laboratory 
of  Plant  Pathology  in  southern  California  and  some  of  our  observa- 
tions are  given  in  detail  in  another  part  of  this  bulletin. 

Host. — The  natural  occurrence  of  bacteriosis  or  walnut  blight  is 
probably  confined  to  the  English  walnut,  or  its  hybrids  with  the  blacks. 
Blighted  nuts  have  been  collected  from  a  Paradox  walnut  tree  (a  hybrid 
of  English  and  California  black)  and  the  organism  has  also  been 
isolated  from  the  leaves  of  Paradox  seedlings  growing  in  the  Experi- 


Bulletin    231]  WALNUT    CULTURE   IN    CALIFORNIA.  321 

merit  Station  nursery.  The  disease  has  never  been  found  on  the  straight 
California  black  or  on  Royal  hybrids,  although  it  can  be  produced 
artificially  by  puncture  inoculation  on  various  species  of  Juglans. 
In  one  instance  a  case  of  blight  infection  was  observed  in  the  nursery 
on  the  leaves  of  California  black  seedlings  near  a  badly  diseased 
branch,  caused  by  artificial  puncture  inoculations.  It  is  probable  that 
these  leaves  were  infected  from  the  disease  on  the  branches. 

Popular  Name  of  Disease. — Newton  B.  Pierce  first  described  this 
disease  as  walnut  bacteriosis,  but  locally  it  is  also  known  as  walnut 
blight.  In  this  paper,  however,  the  more  suggestive  term  Bacteriosis 
will  be  used  for  the  most  part. 

Geographical  Distribution. — It  is  not  definitely  known  just  how 
widely  spread  this  disease  may  be.  In  the  United  States  it  is  found 
more  or  less  scattered  over  California,  some  localities  being  more 
severely  infected  than  others,  due  either  to  climatic  conditions  or  to 
the  disease  not  yet  having  obtained  a  foothold.  California  has  had 
the  disease  for  a  quarter  of  a  century,  and  now  it  is  beginning  to  show 
itself  in  Oregon.1  The  disease  has  also  been  reported  from  Texas,2 
and  is  said  there  to  attack  nearly  every  year  all  the  native  nuts  of  the 
walnut  family.  This  Texas  trouble  has  not  yet  been,  with  certainty, 
identified  as  the  same  disease  as  the  walnut  bacteriosis  in  California. 
Diseased  walnut  leaves  have  been  received  from  at  least  one  point  about 
midway  down  the  Pacific  coast  of  Mexico.  Prom  this  diseased  material 
typical  walnut  blight  cultures  were  grown.  The  walnut  trees  were, 
however,  imported  from  California.  This  disease  will  probably  appear 
wherever  the  English  walnut  can  be  commercially  grown  in  the  United 
States,  and  the  only  reason  that  it  is  of  no  economic  importance  in  the 
Southern  and  Eastern  States  is  because  the  walnut  industry  has  not 
yet  been  developed  there.  In  foreign  countries  the  disease  has  been 
reported  from  New  Zealand.*  California  walnut  growers  who  have 
visited  France  report  having  seen  our  trouble  on  French  walnut  trees. 
Too  much  reliance  cannot,  however,  be  placed  on  these  observations 
because  of  a  fungus  disease  {Marsonia  juglandis)  that  produces  quite 
a  similar  appearance  to  that  of  our  walnut  blight.  (See  description  of 
Marsonia  juglandis,  page  325.  The  testimony  of  these  growers  is, 
however,  strengthened  by  certain  observations  of  our  own.  In  1907 
walnut  scions  were  imported  from  France,  and  among  these  were  several 
that  had  what  appeared  to  be  typical  walnut  blight  lesions.     Cultures 


*C,  I.  Lewis,  Oregon  Experiment  Station,  Bui.  No.  92,  p.   19. 

2G.  E.  Schattenberg,  Texas  Department  of  Agriculture,  Bui.  No.  2,  pp.  42-43. 

*W.  A.  Boucher,  New  Zealand  Department  of  Agriculture,  Report  1900,  pp.  334-335. 

T.  W.  Kink,  New  Zealand  Department  of  Agriculture,  Report  1907,  p.  167. 

14—231 


322  UNIVERSITY   OF    CALIFORNIA EXPERIMENT   STATION. 

were  made  from  these  diseased  scions,  but  from  the  limited  material  at 
hand  no  true  walnut  blight  organism  was  isolated.  These  scions  were 
grafted  into  black  walnut  trees  and  in  the  new  growth  from  some  of 
the  scions  typical  walnut  bacteriosis  appeared  close  to  the  old  wood  of 
the  scion,  although  there  was  no  walnut  blight  in  the  vicinity,  local 
scions  did  not  develop  the  disease,  and  on  the  shoots  from  the  French 
scions  blight  developed  only  close  down  to  the  original  imported  wood. 
While  the  evidence  seems  to  indicate  that  this  disease  may  have  been 
introduced  from  France,  we  have  found  no  report  of  its  occurrence  in 
that  country  in  available  literature.  It  may,  however,  be  confused  with 
their  Marsonia,  and  really  occur  there  to  a  limited  extent. 

History  of  Disease  in  California. — The  disease  has  been  known  for  a 
considerable  time  in  California.  The  first  published  account  which  we 
have  found  occurs  in  the  report  of  the  Secretary  of  Agriculture  for 
1893.*  At  that  time  the  true  cause  of  the  trouble  had  not  been  demon- 
strated, although  the  presence  of  a  bacterial  organism  had  been  found 
constantly  associated  with  the  disease,  and  pure  cultures  of  an  organism 
had  been  made  by  Professor  Newton  B.  Pierce,  who  was  then  in  charge 
of  the  Pacific  Coast  Laboratory  of  the  Division  of  Vegetable  Physiology 
and  Pathology  of  the  United  States  Department  of  Agriculture. 

Growers  affirm  that  the  trouble  had  been  known  for  several  years 
before  this  time.  According  to  local  accounts,  it  appears  that  the  dis- 
ease first  became  noticeable  in  the  principal  walnut  districts  of  Los 
Angeles  County  about  1891.  The  disease  occurred  then  in  a  very  limited 
way  and  seems  to  have  attracted  attention,  not  on  account  of  the  extent 
of  its  ravages,  but  simply  from  the  fact  that  it  was  something  new. 
Growers  who  observed  the  blight  at  that  time  claim  that  its  occurrence 
coincided  with  the  distribution  of  trees  from  a  certain  nursery  in  Orange 
County,  the  proprietor  of  which  nursery  imported  walnut  trees  from 
France  a  few  years  previous.  Whether  or  no  these  statements  are  cor- 
rect, it  appears  to  be  undoubtedly  true  that  the  blight  was  first  noticed 
in  Los  Angeles  County  about  1891,  that  it  came  thence  from  Orange 
County,  and  that  the  disease  then  spread  northward  to  Ventura  and 
Santa  Barbara  counties  until  at  present  it  occurs  in  practically  all  parts 
of  the  State  where  walnut  trees  exist. 

Walnut  bacteriosis  is  by  far  the  most  prevalent  in  the  older  walnut 
sections.  Some  differences  as  to  amount  and  severity  can,  of  course,  be 
noted  in  different  places,  due  either  to  different  climatic  conditions  or 
to  the  fact  that  the  disease  has  not  yet  been  introduced.  The  newer 
groves  that  are  now  being  grown  in  central  and  northern  California  are 


'Report  of  Secretary  of  Agriculture,  Division  of  Vegetable  Pathology,  1893,  p.  273. 


Bulletin   231]  WALNUT   CULTURE   IN   CALIFORNIA.  323 

at  present  only  troubled  with  this  disease  to  a  limited  extent.  In 
northern  California  and  Oregon  there  are  few  commercial  bearing 
groves  at  the  present  time.  This  disease  shows  the  greatest  variation  in 
the  amount  of  infection  from  year  to  year,  and  while  it  may  seem  to  be 
scattered  throughout  a  grove,  yet  there  are  trees  here  and  there  that 
are  almost  free  from  attack.  Some  years  there  is  almost  no  blight  or 
only  a  small  amount  of  early  infection.  There  is  less  infection  in  a 
bright  spring  that  is  free  from  fogs  and  cloudy  days. 

The  disease  is  now  distributed  all  over  California,  being  often  found 
even  upon  isolated  walnut  trees  situated  a  long  distance  from  any  others 
of  the  same  kind.  It  has  no  doubt  been  generally  disseminated  through 
nursery  stock,  which  is  often  infected,  and  may  also  be  carried  through 
the  air.  Localities  with  much  foggy  or  moist  weather  during  the  spring 
show  the  most  severe  attacks  of  blight,  but  in  places  where  the  crop  is 
largely  grown,  as  in  the  southern  part  of  the  State,  the  disease  becomes 
more  conspicuous,  although  it  is  really  more  prevalent  and  virulent  in 
some  other  parts  of  the  State  where  the  walnut  crop  is  less  important. 
The  occurrence  of  the  disease  varies  everywhere  in  direct  proportion  to 
the  amount  of  atmospheric  moisture  during  the  spring  and  early  sum- 
mer months,  from  the  time  the  trees  start  into  growth  until  the  nuts 
are  well  advanced  in  development.  The  amount  of  blight  likely  to  occur 
in  a  given  locality  or  given  season  can  be  closely  estimated  on  this  basis, 
as  the  connection  between  the  occurrence  of  the  disease  and  the  amount 
of  atmospheric  moisture  is  well  established.  Localities  with  much  spring 
and  summer  fog  may  expect  a  considerable  development  of  walnut 
blight,  while  those  where  such  weather  does  not  prevail  may  safely  count 
upon  being  reasonably  free  from  this  trouble,  even  though  it  be  fre- 
quently introduced.  The  same  rule  applies  as  to  the  occurrence  of  the 
disease  in  different  seasons. 

Losses  from  Blight. — The  amount  of  loss  actually  caused  by  this  dis- 
ease has  been  every  year  very  large  for  the  past  ten  years  or  more,  but 
has  varied  considerably  from  year  to  year.  It  is  also  true  that  much 
has  been  attributed  to  blight  which  in  reality  had  nothing  to  do  with 
this  disease,  such  as  the  effects  of  drouth,  frost  and  other  unfavorable 
climatic  or  soil  conditions.  At  the  same  time  the  losses  directly  attribu- 
table to  blight  have  been  extremely  large.  One  significant  fact  in  this 
connection  is  that  while  the  walnut  acreage  in  southern  California  has 
multiplied  many  times  during  the  past  decade,  the  total  walnut  crop  of 
the  State  has  increased  very  little  during  this  time.  In  fact,  the  crop 
has  been  actually  much  less  during  several  years  of  this  period  than  it 
was  in  some  of  the  best  years  of  the  preceding  decade.  This  loss  or 
failure  of  the  crop  to  increase  has  not  been  entirely  attributable  to 
blight,  yet  it  has  certainly  been  due  to  the  disease  much  more  than  to 


324  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

any  other  one  factor.  In  the  year  1903,  one  of  the  first  bad  blight  years, 
the  total  crop  of  the  State  fell  off  to  only  a  little  more  than  one  half 
of  that  of  the  previous  year.  It  is  probably  conservative  to  state  that 
in  the  seedling  groves  of  southern  California  an  average  loss  of  at  least 
50  per  cent  of  the  crop  which  would  otherwise  have  been  harvested  has 
been  caused  by  the  blight  during  the  past  ten  years.  Many  individual 
trees  may  be  seen  some  years  which  show  a  loss  of  practically  all  the 
crop  from  blight.  This  disease  affects  the  quantity  and,  to  some  extent, 
the  quality  of  the  crop  much  more  than  it  does  the  growth  of  the  tree, 
being  of  less  importance  in  that  respect  than  pear  blight,  for  instance, 
and  many  other  plant  diseases.  While  the  leaves  and  young  shoots 
become  affected  to  some  extent,  as  we  shall  describe  later,  this  injury 
in  otherwise  thrifty  trees  is  soon  overcome  during  seasons  when  the  dis- 
ease is  less  prevalent,  and  is  not  usually  a  serious  matter.  In  occasional 
instances,  especially  on  light,  dry  soils  where  the  trees  are  at  best  none 
too  thrifty,  sufficient  twig  infection  sometimes  occurs  to  actually  stunt 
and  dwarf  the  trees  to  a  considerable  extent  by  a  continual  killing  back 
of  the  young  twigs.  Damage  is  also  done  in  such  cases  by  the  loss  of 
the  fruit  spurs  which  should  produce  the  catkins  and  nut-bearing  shoots 
the  following  year. 

It  should  be  clearly  understood  that  walnut  blight  is  not  conspicu- 
ously a  die-back  disease  of  the  tree,  but  is  more  especially  a  source  of 
loss  in  the  amount  of  the  crop,  varying  widely  in  prevalence  from  year 
to  year,  and  not,  in  the  majority  of  instances,  seriously  affecting  the  life 
or  growth  of  the  tree. 

Earlier  Studies. — Reference  has  already  been  made  to  the  work  done 
by  Pierce.  He  first  isolated  the  organism  and  printed  quite  a  full  and 
accurate,  technical  description1  of  the  disease  and  its  physiological  and 
pathological  characteristics.  He  also  published  several  more  popular 
accounts  of  the  trouble.2  Various  experiments  in  spraying  were  made 
by  him  in  trying  to  control  the  trouble  by  such  means,  the  results  of 
which  will  be  more  fully  discussed  under  another  heading.  He  also 
observed  that  certain  walnut  trees  seem  to  possess  a  certain  immunity 
to  the  disease,  but  did  not  indicate  that  the  time  of  blooming  had  any- 
thing to  do  with  the  amount  of  blight  that  developed. 

In  1905  the  California  legislature  made  a  special  appropriation  to 
the  Experiment  Station  for  carrying  on  an  investigation  of  this  disease, 
and  Mr.  A.  M.  West  was  appointed  to  work  on  the  problem.  He  isolated 
and  studied  the  organism  and  confirmed  in  most  respects  the  work 
previously  done  by  Pierce. 


botanical  Gazette,  1901,  31,  p.  273. 

2PacifLc  Rural  Press,  1896,  57,  No.  25,  p.  387. 

California  Fruit  Grower,  1896,  19,  Nos.  13,  p.  243;  16,  p.  316. 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  325 

The  work  here  recorded  covers  the  results  of  previous  investigators, 
verifying  them  in  most  cases,  while  some  new  data  has  also  been  added. 

Cause  of  Disease. — The  disease  thus  far  discussed  has  been  con- 
clusively proven  to  be  produced  by  a  species  of  bacteria  growing  in 
the  diseased  parts,  and  hence  is  very  properly  referred  to  as  Bacteriosis. 
A  microscopic  examination  of  diseased  tissue  shows  countless  numbers  of 
these  small,  rod-shaped  organisms  to  be  present.  By  employing 
bacteriological  methods  pure  cultures  of  these  germs  were  obtained  and 
then  these  pure  cultures  were  used  in  making  artificial  inoculations  into 
healthy  nuts  and  shoots,  thus  again  producing  the  typical  disease.  The 
organism  has  been  isolated  many  times,  and  no  difficulty  has  been 
experienced  in  always  producing  the  disease  by  inoculation  from  culture 
if  the  tissue  was  in  an  active  growing  condition. 

The  walnut  blight  organism  belongs  to  what  are  called  the  bacteria; 
low  forms  of  plant  life  that  are  extremely  small  in  size  and  increase 
rapidly  in  number  by  elongation  and  division  or  fission.  When  grown 
in  artificial  cultures  in  mass  they  have  a  shiny  yellow  appearance. 

Confusion  with  Marsonia  juglandis.- — It  is  important  to  refer  to  this 
trouble  in  some  detail  for  it  has  been  confused  with  our  walnut  bac- 
teriosis and  bears  a  close  resemblance  to  it  in  very  many  respects.  This 
disease  is  caused  by  a  fungus  that  is  not  uncommon  in  the  Eastern 
States  on  the  leaves  of  the  butternut,  Juglans  cinerea,  and  on  the  leaves 
of  the  black  walnut,  Juglans  nigra.  So  far  as  our  observations  have 
gone  the  trouble  does  not  affect  the  nuts  or  branches  of  these  trees.  In 
France  the  fungus  occurs  on  the  nuts  of  the  English,  walnut  as  well  as 
on  the  branches,  causing  them  to  have  a  black  appearance,  like  our 
Bacteriosis.  This  disease  is  described*  by  Prillieux  and  Delacroix  of 
the  Institute  National  Agronomique ,  and  Laboratoires  de  Pathologie 
Vegetale.  No  mention  in  this  article  or  any  other  scientific  literature  is 
made  of  our  Bacteriosis  occurring  in  France. 

In  California  no  species  of  Marsonia  is  known  to  occur  on  English 
walnuts.  There  is  a  species  of  Marsonia  recorded  by  A.  D.  McClat chief 
as  occurring  on  the  leaves  of  Juglans  calif  ornica,  but  this  trouble  is  not 
at  all  common.  In  the  spring  of  1910  a  species  of  Gloeosporium  was 
found  attacking  the  leaves  of  Juglans  calif  ornica.  This  occurred  only 
on  the  leaves  and  could  not  be  confused  with  the  Marsonia  referred  to 
in  the  following  paragraph : 

The  following  is  an  abstract  from  the  article  by  Prillieux  and  Dela- 
croix: Marsonia  juglandis  (anthracnose)  is  parasitic  on  leaves,  young 
shoots  and  fruits  of  the  Juglans  regia.     The  disease  forms  round  spots 


♦Maladies  des  Plantes.  Les  Maladies  des  Noyers  en  France, 
f Seedless  Plants  of  Southern  California,  p.  378. 


326  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

on  leaves,  yellowish  brown  in  color  on  the  upper  surface,  and  grayish 
brown  on  the  under  side.  Hemispherical  masses  appear,  the  acervuli,  as 
little  pulverulent  brownish  bodies. 

On  the  young  shoots  the  color  of  the  diseased  portions  is  far  different. 
Spots  are  irregular,  shrunken,   with  edges  more  highly  colored  and 


Fig.  78. — Bacteriosis   on   green   shoots   of   English   walnut. 

thicker,  bearing  the  pulverulent  cushions  of  the  fungus.  The  appear- 
ance of  the  disease  on  the  shoots  is  a  canker,  reminding  me  of  the  true 
anthracnose  of  the  grapevine. 

Upon  the  fruits  the  parenchyma  of  the  epicarp  is  invaded  in  its  entire 
thickness  by  the  parasite.     The  cankers  on  the  fruit  are  browner  than  on 


Bulletin    231]  WALNUT    CULTURE   IN    CALIFORNIA. 


327 


Fig.   79. — Bacteriosis  on  green  shoots. 


328  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

the  shoots  and  are  more  spread  out  over  the  surface.  The  disease  does 
most  serious  damage  on  the  fruit  and  is  worse  in  wet  seasons  and  in 
certain  valleys.  If  the  disease  starts  early  the  nuts  remain  small  and 
undeveloped  and  the  amount  of  fruit  is  greatly  reduced.  The  disease 
is  frequent  in  walnut-growing  sections  of  France.  Bordeaux  mixture 
has  been  tried  for  this  disease  and  while  it  proved  somewhat  successful, 
yet  it  was  too  costly  and  difficult  to  apply. 

Characteristics  of  Bacteriosis. — Walnut  bacteriosis  may  occur  on  all 
the  tender,  new,  growing  parts  of  the  tree,  such  as  young  nuts  and 
branches,  the  petioles  of  leaves,  as  well  as  midveins,  the  fine  lateral  veins 
and  adjoining  parenchyma.  On  the  affected  parts  characteristic  blackish 
colored  areas  or  quite  pronounced  lesions  are  produced.  The  blackening 
is,  as  Fierce  suggests,  brought  about  by  oxidation  of  the  tannic  acid  in 
the  tissue.  At  any  point  of  injury  in  the  tender  growth  of  the  walnut 
a  very  similar  black  coloration  will  occur. 

On  Branches. — Bacteriosis  is  at  first  confined  to  small  areas,  but  under 
favorable  conditions  these  increase  in  size  to  a  lesion  or  diseased  area 
extending  two  or  three  inches  in  length  on  the  green  shoot.  The  disease 
always  has  its  beginning  on  the  young  succulent  growth  which  may  be 
near  the  growing  end  or  at  any  other  point.  When  the  disease  infects  a 
branch  near  its  end,  that  part  may  be  killed  back,  but  this  seldom  occurs 
except  when  the  diseased  lesion  is  very  near  the  end.  In  the  worst  dis- 
eased lesions  the  tissue  is  killed  inwardly  to  the  pith,  while  in  less  severe 
cases  only  the  bark  and  wood  are  diseased.  As  the  shoot  becomes  more 
woody  sit  is  more  and  more  difficult  to  infect  and  no  tissue  ever  becomes 
affected  after  the  first  few  months  of  its  growth.  The  disease  after  the 
first  year,  even  in  well  defined  lesions,  gradually  dies  out  and  the  tissue 
heals  over  the  old  lesion,  although  in  some  cases  short  lengths  of  the 
worst  diseased  shoots  may  die  back  for  a  few  inches.  The  diseased 
portion  on  the  twig  at  first  forms  a  small,  discolored  or  water-soaked 
area  which  gradually  increases  in  size,  and  at  length  the  central  portion 
is  black  and  is  surrounded  by  a  water-soaked  margin  or  fermentation 
zone.  As  the  shoot  becomes  more  and  more  woody  the  active  develop- 
ment of  the  disease  is  checked  and  no  further  tissue  is  involved.  Then 
the  whole  diseased  area  becomes  blackened  in  color.  The  diseased  por- 
tion in  many  cases  comes  to  have  a  somewhat  shrunken,  dried-out, 
deformed,  cracked  condition  because  of  the  killing  and  drying-out  of 
the  tissue. 

During  the  spring  when  the  flow  of  sap  is  active  there  is  often  quite  an 
accumulation  of  liquid  in  the  pith  cavity  beneath  very  badly  diseased 
lesions.     This  liquid  has  been  tested  at  different  times  to  see  if  this  was 


*  "Diseases  of  Walnuts,"  Bailey's  Encyclopedia  of  Horticulture. 


Bulletin    231]  WALNUT    CULTURE   IN    CALIFORNIA.  329 

a  source  of  infection.  The  test  did  not  seem  to  show  that  the  blight 
organism  was  present  in  any  great  abundance  in  this  liquid.  Pierce 
states*  that  the  blight  organism  winters  in  the  pith  cavity,  but  we  have 
not  found  the  organism  any  more  abundant  in  this  place  than  in  the 
partly  live  wood  and  bark  of  the  diseased  lesion.  The  diseased  twigs  of 
the  previous  year  are  without  doubt  the  chief  source  of  the  initial  infec- 
tion each  spring.  From  our  study  we  believe  the  old  lesions  to  be  the 
only  place  where  the  organism  can  live  over  the  dormant  period  of 
winter  and  start  the  first  infection  the  following  spring,  although  Pierce 
states  that  the  old  nuts  and  soil  are  a  source  of  infection. 

Bacteriosis  is  not  Die-Back. — Walnut  blight  causes  very  characteristic, 
comparatively  small,  sunken?  black  areas  on  the  small  shoots  of  the  tree. 
It  does  not  attack  branches  of  any  size  and  does  not  injure  them  to  such 
an  extent  that  they  die  back  for  several  feet,  as  in  the  case  of  die-back. 
See  Die-Back,  page  372. 

On  Nursery  Trees.— Bacteriosis  is  especially  severe  in  rapid-growing 
trees  in  the  nursery.  Walnuts  $re  grown  ior  two  years  in  the  nursery, 
being  grafted  the  second  season.  The  scions,  after  they  start,  usually 
grow  rapidly  and  are  in  a  very  favorable  condition  for  this  disease  to 
attack  them.  This  infection  in  many  cases  comes  from  using  diseased 
scions.  Rapid  sucker  growth  in  the  orchard  is .  very  apt  to  become 
infected  and  show  the  disease  in  a  manner  similar  to  that  which  occurs 
in  nursery  trees. 

Leaves. — The  leaves  are  sometimes  diseased,  especially  the  petioles  and 
veins,  which  become  a  blackish  or  brownish  color.  The  disease  also 
attacks  the  parenchyma  or  soft  tissue  of  the  leaf,  causing  spots  of  a 
brownish  color  and  of  various  shapes.  These  spots  are  rather  common 
on  rapidly-growing  leaves,  and  especially  on  the  very  large  leaflets  of 
young  nursery  trees.  The  spots  are  circular  or  angular  in  outline  and 
by  confluence  often  cause  quite  large  diseased  areas.  Here  the  small 
lateral  veins  in  the  diseased  areas  are  a  browner  color  than  healthy  ones. 
Fig.  80.  The  disease  does  not  cause  serious  defoliation  of  the  tree  and 
should  not  be  confused  with  the  falling  of  the  leaves  that  sometimes  takes 
place  after  a  period  of  hot  weather  during  the  summer  months. 

Catkins. — The  catkins  are  probably  not  diseased  by  walnut  bacteriosis. 
They  often  turn  black,  but  this  is  probably  only  due  to  the  natural 
process  of  dying  and  drying  up  after  their  work  is  done.  Various 
attempts  have  been  made  to  obtain  the  blight  organism  from  these  dark- 
ened catkins,  but  without  success. 

Nuts. — Bacteriosis  on  the  young  nuts  is  especially  virulent  and 
destructive  under  favorable  conditions.     The  disease  on  the  twigs  and 


*Paciflc  Rural  Press,  1899;  Vol.   57,  No.  25,  p.  387. 


330 


UNIVERSITY   OF   CALIFORNIA — EXPERIMENT   STATION. 


leaves  ordinarily  does  very  little  injury  and  the  disease  would  be  of 
little  economic  importance  did  it  not  attack  the  nuts.  Many  of  these 
may  become  diseased  and  fall  when  they  are  one  eighth  to  one  half  an 


Fig.   80. — Bacteriosis  on  leaves. 


inch  in  diameter,  and  continue  to  drop  more  or  less  all  through  the 
summer.  Pierce  estimated  a  loss  of  from  50  to  80  per  cent  in  badly 
diseased  groves.     We  have  never  made  a  careful  estimate  of  the  loss 


Bulletin    231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


331 


in  actual  per  cents,  but  know  that  it  is  very  heavy  in  some  groves  when- 
ever the  disease  is  severe.  The  loss  may,  however,  be  more  apparent 
than  real,  especially  when  there  is  a  heavy  crop,  as  the  relieving  of  the 


Fig. 


-Walnuts    affected   by   Bacteriosis,    mostly   stigma   or   blossom-end    infection. 


tree  of  a  part  of  its  load  will  better  fit  it  to  bear  a  good  crop  the  follow- 
ing year,  instead  of  periodic  heavy  and  light  crops.  For  the  past  few 
years,  in  spite  of  this  disease,  there  have  been  good  crops  of  nuts. 


332 


UNIVERSITY   OF    CALIFORNIA EXPERIMENT   STATION. 


Young  trees  are  much  more  free  from  bacteriosis  than  are  those  that 
have  been  in  bearing  for  a  longer  time. 

It  should  be  remembered  that  other  causes  than  bacteriosis  may  make 
the  small  nuts  fall,  as  for  instance  poor  pollination,  which  may  result 
from  a  lack  of  pollen  or  unfavorable  climatic  conditions,  the  small  nuts 
being  very  susceptible  to  cold  at  this  time.  In  the  English  walnut  the 
catkins  and  nuts  are  produced  in  the  spring  in  separate  clusters  on  the 
same  tree.  (See  Fig.  1.)  The  catkins  are  the  male  flowers  and  bear 
the  pollen.  They  are  always  found  on  the  old  wood,  and  these  may  be 
seen  as  rather  long  buds  in  the  late  autumn.  The  small  nuts  are  found 
on  the  new  growth.    These  two  kinds  of  flowers  should  appear  at  about 


Fig.   82. — Half-grown   walnuts   affected   with   Bacteriosis. 

the  same  time,  but  on  the  seedling  trees  there  is  the  greatest  variation. 
A  tree  may  have  a  very  limited  number  of  catkins  or  may  be  abundantly 
provided.  These  may  appear  at  the  same  time  as  the  nuts,  or  too  early 
or  late  to  be  of  much  service  in  fertilizing  them. 

Blossom  End  Infection. — While  the  nuts  may  be  infected  at  any 
point  in  the  surface,  by  far  the  most  common  as  well  as  most  virulent 
form  of  infection  is  at  the  blossom  end  near  what  is  technically  called 
the  stigma.  This  is  the  weakest  part  of  the  nut  and  is  especially  sensitive 
to  the  blight.  The  bacteriosis  is  very  bad  on  the  small  nuts,  and  when 
once  it  has  started  at  this  point  it  rapidly  continues  its  growth  within 
the  tissue,  until  the  small  nut  is  sufficiently  weakened  to  fall.    Not  all 


Bulletin    231]  WALNUT    CULTURE   IN    CALIFORNIA.  333 

the  infected  nuts  fall  when  they  are  small,  but  some  remain  on  even  until 
harvest  time.  In  the  nuts  the  disease  gradually  grows  within  the  tissue 
until  the  kernel  is  reached  which  at  length  becomes  blackened  and  then 
destroyed.  The  disease  may  start  at  any  place  on  the  nut  and  gradu- 
ally extend  through  other  tissues  into  the  kernel,  but  by  far  the  most 
of  the  infections  that  injure  the  kernel  are  from  the  blossom  end. 

Lateral  Nut  Infection. — The  disease  on  the  nuts  starts  at  one  or  more 
points  on  the  surface  as  a  small,  circular,  raised,  discolored  area  that 
at  first  has  a  water-soaked  appearance  and  may  not  be  larger  than  the 
point  or  head  of  a  pin  when  first  visible.  The  diseased  area  in  its 
earliest  stages  is  slightly  raised  above  the  surrounding  healthy  tissue, 
but  as  the  disease  progresses,  the  spot  becomes  more  or  less  sunken  below 
the  normal  tissue.  The  spot  gradually  enlarges  in  size  and  becomes 
black  in  appearance.  Surrounding  the  blackened  area  is  a  paler  zone, 
having  the  same  water-soaked  appearance  already  referred  to.  This 
band  of  tissue  lies  between  the  healthy  tissue  and  the  blackened  area 
and  represents  the  cells  of  the  tissue  that  are  being  acted  upon  by  the 
ferments  secreted  by  the  organism,  which  break  down  the  tissue  and 
prepare  the  way  for  the  further  advance  of  the  bacteria.  In  the  early 
infection,  if  climatic  conditions  are  favorable,  lesions  or  dark  spots  are 
formed  which  often  extend  through  the  hull  and  shell-forming  tissues 
into  the  kernel.  The  nut  in  such  cases  is  deformed  in  shape  as  the 
diseased  part  ceases  to  grow.  Such  nuts  do  not  bark  clean,  as  the  outer 
covering  clings  very  tightly  to  the  shell,  and  the  kernel  at  best  is  only 
poorly  developed.  Such  nuts  are  usually  never  picked  up  from  the 
ground,  and  in  any  case  are  only  fit  for  culls. 

Late  Infections. — It  often  happens  that  during  the  summer  months 
weather  conditions  are  favorable  for  natural  infection  of  nuts.  At 
this  time  the  outer  tissue  is  beginning  to  harden  and  is  not  in  condition 
for  the  deep  growth  of  the  disease  that  occurs  earlier  in  the  season  when 
the  tissue  is  more  tender.  Then,  too,  the  disease  may  start  in  the  sur- 
face rather  late  in  the  season  and  suddenly  conditions  become  unfavor- 
able for  its  further  development,  thus  giving  a  very  shallow,  superficial 
development  of  the  disease.  These  points  of  infection  appear  as  small, 
dark-colored  areas  scattered  over  the  surface  of  the  nut.  Each  little 
infection  can  be  distinctly  seen,  or  its  confluence  with  others  may  make 
a  large  spot.  In  these  late  infections  the  development  is  shallow  and 
does  not  penetrate  much  through  the  epidermis,  and  the  disease  seems 
to  dry  out  and  die.  Occasionally  a  more  severe  case  of  late  infection 
occurs  where  the  blackening  and  lesion  extend  to  the  hard  shell,  causing 
the  hull  to  cling  to  the  shell  of  the  nut. 


334  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION. 


Fig.   83. — Walnuts  with  late  infection  by  Bacteriosis. 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  335 

White  Deposit  on  Diseased  Tissue.  —  On  the  surface  of  the  diseased 
tissue  of  both  the  branches  and  the  nuts  can  often  be  observed  a  whitish 
substance  that  accumulates  during  the  summer  but  at  length  disappears. 
When  this  is  properly  stained  and  examined  with  a  compound  micro- 
scope, it  is  found  to  be  composed  of  countless  numbers  of  bacteria  and 
broken-down  plant  tissue.  Cultures  made  from  this  substance  gave  a 
large  number  of  typical  walnut  disease  colonies.  A  somewhat  careful 
study  was  made  of  this  white  deposit  in  small  nuts.  Small  diseased 
nuts  having  this  white  substance  were  put  in  10  per  cent  chromic  acid 
and  the  deposit  swelled  up  and  became  soft  and  gum-like.  It  is  thought 
that  this  white  substance  containing  so  many  organisms  is  an  important 
source  of  natural  infection.  Larger  nuts,  diseased  at  the  blossom  end, 
sometimes  show  gum-like  streaks  running  down  over  the  nut  from  the 
diseased  portions.  This  substance  also  was  found  to  contain  bacterial 
organisms.  From  laboratory  experiments  it  is  known  that  the  organism 
is  quite  resistant  to  desiccation  and  probably  the  condition  described 
is  an  important  factor  in  bringing  this  about. 

Winter  Habitat  of  Germ. — The  germ  of  the  organism  without  question 
winters  in  the  old  lesions  of  the  branches.  Much  work  has  been  done 
in  making  cultures  at  short  intervals  of  time  throughout  the  year  from 
the  different  diseased  tissues  in  order  to  see  if  the  disease  organism  wTas 
alive  and  where  it  best  could  pass  through  the  winter  or  dormant  period. 
This  work  of  making  artificial  cultures  is  given  more  in  detail  on  page 
343.  The  work  began  in  October,  1907,  and  continued  until  the  follow- 
ing spring,  at  which  time  the  disease  again  appeared  on  the  new  growth. 
In  every  series  of  cultures  the  disease  organism  was  found,  showing 
conclusively  that  the  disease  was  still  alive  in  the  old  lesions  of  the  wood 
and  bark.  The  cultures  made  from  the  old  nuts,  both  those  on  the 
ground  and  some  still  on  the  tree,  gave  some  walnut  blight  cultures 
early  in  the  autumn,  but  as  the  season  advanced  the  organism  seemed 
to  die  out  and  toward  spring  it  was  almost  impossible  to  secure  blight 
cultures  from  the  old  nuts  found  about  the  orchard.  Pierce*  states  that 
the  organism  "  winters  in  fallen  nuts  beneath  the  trees  and  probably 
upon  fallen  leaves  and  upon  the  soil."  We  believe  that  the  old  nuts 
are  not  an  important  source  of  infection,  since  in  all  well-cared-for 
groves  these  are  plowed  under  before  the  tree  starts  out  in  leaf.  This 
is  especially  true  of  those  groves  where  a  cover  crop  is  sown.  We  have 
never  tested  soil  and  leaves  to  see  if  the  germ  could  be  found  wintering 
in  them. 

The  most  prolific  source  of  new  infection  is  the  lesions  on  diseased 
twigs.  Here  the  germs  remain  in  almost  a  dormant  condition  until  the 
warm  weather  of  spring,  which  arouses  them  to  a  renewed  activity,  when 
they  exude  on  the  surface  and  are  carried  to  the  new  growth,  leaves, 


*  Pacific  Rural  Press,  Vol.  57,  No.  25,  p.  387. 


336  UNIVERSITY   OF    CALIFORNIA EXPERIMENT   STATION. 


Fig.   84. — Above — Sections  of  two  walnuts  with  Bacteriosis  at  the  left,  two 
normal  nuts  at  the  right.     Below — Old,   blighted  nuts. 


Bulletin    231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


337 


branches  and  nuts.  From  our  observation,  the  young  leaves  seem  to  be 
infected  very  early  and  probably  are  one  of  the  chief  sources  of  the 
secondary  infection. 

Secondary  Infection. — The  first  or  initial  infection  may  occur  on  only 
a  few  nuts  and  new  growth,  then  quite  suddenly  the  disease  seems  to 
spread  and  infect  many  small  nuts.  This  sudden  increase  of  the  disease 
is  due  to  an  infection  from  the  earlier  diseased  nuts  and  new  growth, 
and  can  thus  be  termed  the  secondary  infection. 

Effect  of  Climate. — Walnut  bacteriosis  is  a  disease  that  is  quite 
susceptible  to  variations  in  climatic  conditions.     It  is  a  matter  of  com- 


Fig.   85. — Bacteriosis  lesions  on  older  wood.      Healing  over. 

mon  observation  among  growers  that  the  amount  of  blight  varies  from 
year  to  year  in  a  given  locality,  also  that  some  sections  are  freer  from 
the  disease  than  are  others,  even  during  the  same  periods  of  time.  A 
given  grove  may  be  very  bad  one  year  and  nearly  free  from  the  disease 
the  following  year.  This  is  well  illustrated  by  a  comparison  of  the  years 
15—231 


338  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

1907  and  1908.  In  1907  there  was  an  abundant  amount  of  bacterial 
infection  and  quite  a  severe  loss  of  nuts.  There  was  at  the  same  time  a 
large  crop  of  nuts.  In  1908  there  was  almost  an  absence  of  blight  and 
a  very  much  lighter  crop  of  nuts.  It  is  rather  difficult  to  always  fully 
account  for  these  variations  because  of  the  great  number  of  conditions 
that  must  be  considered. 

Fogs  and  Moisture. — The  amount  of  moisture  present  in  the  air  has 
without  question  considerable  influence  on  the  quantity  of  disease  that 
may  develop,  as  humid  conditions  are  especially  favorable  for  its  spread. 
It  has  been  proven  again  and  again  by  our  experiments  that  infection  is 
produced  when  water  containing  the  disease  germs  is  sprayed  on  the 
surface  of  the  young  nuts,  while  the  untreated  ones  are  free  from  the 
disease.  Then,  for  infection  to  take  place  under  natural  conditions,  it 
only  becomes  necessary  for  virulent  germs  to  come  in  contact  with 
immature  nuts,  and  water  is  apparently  the  principal  agent  in  convey- 
ing the  germs  from  the  diseased  lesions  to  the  young  growth  or  small 
nuts  below.  Rains  very  rarely  occur  in  the  spring  after  the  nuts  appear, 
but  foggy  weather  is  often  more  or  less  frequent.  What  are  called  high 
fogs,  a  cloudy  condition  of  the  sky,  but  with  little  moisture,  which  in 
some  sections  occur  during  the  spring  months,  do  not  cause  infection, 
although  such  cloudy  conditions  are  favorable  for  bacteriosis  to  develop 
where  infection  has  already  taken  place.  Low  fogs  and  especially  foggy 
nights  are  very  favorable  for  the  dissemination  and  new  infection  of 
the  small  nuts.  During  one  of  these  fogs  the  trees  become  saturated, 
water  dripping  from  one  portion  of  the  tree  to  another  which  could 
easily  carry  the  disease  organisms  to  healthy  tissue.  Observations  go  to 
show  that  the  secondary  infection,  in  which  large  numbers  of  the  small 
nuts  become  diseased,  is  very  likely  to  follow  one  of  these  foggy  periods. 

Insects. — It  is  more  difficult  to  say  just  what  part  insects  play  in  the 
spread  of  this  disease,  as  it  is  not  necessary  for  the  nuts  to  be  bitten  in 
order  to  cause  infection.  Insects  are  present  in  quite  large  numbers 
about  the  tree.  Several  species  of  flies  and  beetles  are  most  numerous. 
Flies  have  been  observed  on  diseased  nuts,  probably  attracted  by  the 
exuding  of  organic  matter  mixed  with  walnut  blight  germs  that  is  some- 
times present,  and  these  flies  have  been  collected  and  culture  media 
inoculated  by  placing  them  in  it,  with  the  result  that  the  characteristic 
organism  has  developed  in  the  cultures.  This  shows  that  the  living 
germs  of  walnut  blight  were  on  their  bodies  and  only  needed  to  be 
placed  in  contact  with  the  nut  to  cause  infection.  A  species  of  aphid 
is  often  abundant  on  the  leaves,  rarely  on  the  nuts  and  branches.  This 
insect,  however,  appears  some  time  after  the  nuts,  and  probably  does 
not  cause  much  infection  of  any  part  of  the  tree  except  possibly  the 
leaves.  The  honeydew  is  secreted  and  deposited  on  leaves  and  nuts, 
and  in  this  a  sooty  mold  grows. 


Bulletin   231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


339 


How  the  Germ  Enters  the  Tissue. — Nuts,  as  well  as  the  leaves  and 
young  shoots,  are  provided  with  stoma t a  or  breathing  pores  through 
the  epidermis  into  the  in- 
terior of  the  tissue.  These 
stomata  on  the  nuts  are  ar- 
ranged in  groups  of  from 
five  to  a  dozen  or  more,  and 
are  to  be  found  on  the  paler 
green  specks  that  spot  the 
surface  of  the  husk  of  the 
green  nuts.  It  is  through 
these  openings  that  the  bac- 
terial organism  can  gain 
entrance  to  the  interior  of 
the  tissue  of  the  young  nuts. 

The  blight  organism  is 
motile  and  when  carried  to 
the  surface  of  the  nut  by 
moisture,  such  as  fogs  and 
heavy  dews,  can  use  this 
moist  surface  to  swim 
directly  into  the  stomata 
or  breathing  pores  just  de- 
scribed. When  once  in  the 
interior  of  the  nut  the  con- 
ditions are  favorable  for 
further  development.  While 
these  stomata  have  the  power 
to  open  and  close,  they  are 
probably  never  so  closely 
shut  that  the  small  germs 
could  not  enter.  The  moist 
conditions  favorable  for  the 
entry  of  the  germ  or  bac- 
terium through  the  stoma 
are  also  just  the  conditions 
necessary  for  keeping  this 
entrance  open. 

Two  Seasons  Compared. — 
The  two  years  of  1907  and 
1908  well  illustrated  the  two 
extremes  of  much  and  practically  no  bacteriosis  of  the  walnut.     The 
year  1907  was  very  favorable  for  the  development  of  this  trouble,  while 


Fig.  86. — Surface  of  green  walnut,  showing  two 
groups  of  stomata  through  which  the  blight 
germ  enters.  Much  enlarged.  Each  group 
represents  one  of  the  light-colored  spots  on 
the  surface  of  the  green  hull. 


340  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

the  following  one  showed  comparatively  little  of  the  disease.  It  will  be 
instructive  to  observe  a  few  of  the  reasons  for  this  difference. 

The  winter  of  1906  and  1907  was  a  rather  wet  season,  there  being 
about  20  inches  of  rainfall  in  the  vicinity  of  Los  Angeles.  The  spring 
opened  very  early,  some  walnut  trees  beginning  to  show  leaves  during 
the  last  week  in  February.  Some  of  our  preliminary  inoculation  work 
was  done  at  this  time,  February  22d.  Small  nuts  appeared  early  in 
March,  and  on  March  7th  we  inoculated  our  first  small  walnuts  for 
bacteriosis.  It  is  safe  to  say  that  the  season  was  at  least  three  weeks  in 
advance  of  the  average  time  of  blossoming,  which  gave  a  longer  period 
favorable  for  infection  to  take  place.  This  is  an  unusual  situation,  and 
has  not  been  repeated. 

The  winter  of  1907  and  1908  was  a  dry  winter,  there  being  about 
twelve  inches  of  rainfall  in  the  regions  around  Los  Angeles.  The  earlier 
trees  began  putting  out  leaves  about  April  1st.  Too  much  importance 
should  not  be  given  to  the  difference  in  the  amount  of  rainfall  of  the 
two  years,  as  its  relation  to  the  amount  of  bacteriosis  is  exceedingly 
doubtful. 

Another  favorable  condition  of  1907  was  the  cloudy  weather  during 
March,  April  and  May,  the  time  of  year  when  the  bacteriosis  is  mnst 
active,  as  compared  with  the  conditions  of  the  same  period  during  the 
following  year.  This  is  well  shown  in  the  following  table  compiled 
from  data  very  kindly  furnished  by  Mr.  A.  B.  Wollaber,  the  local  fore- 
caster of  the  United  States  Government  Weather  Bureau  at  Los  Angeles. 
It  is  well  known  that  sunlight  is  fatal  to  most  kinds  of  bacterial  germs, 
and  the  walnut  bacteriosis  is  no  exception  to  this  rule.  The  table  shows 
that  the  nuts  during  the  spring  of  1908  had  a  much  greater  amount  of 
sunshine  during  their  first  three  months  of  growth  than  did  those  of 
1907  during  the  corresponding  three  months.  May  not  this  in  some 
measure  be  the  reason  for  the  difference  in  the  amount  of  this  disease 
during  these  two  years? 


Bulletin   231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


341 


TABLE   I. 
Showing  average  daily  hours  of  sunlight  for  periods  of  five  days. 


1907. 

1908. 

Date. 

March. 

April. 

May. 

March. 

April. 

May. 

1-5      

5.4 
6.8 
10.0 
5.6 
4.9 
9.8 

7.8 
10.7 
3.3 
8.3 
7.4 
2.9 

6.1 

9.7 

11.5 

11.9 

10.8 

4.8 

7.1 

10.9 

11.8 

5.2 

9.3 

10.6 

10.5 
8.5 

11.3 

11.0 
8.1 

11.6 

i)  8 

6-10    

11-15    ..     . 

12.9 
9  6 

16-20    

12.7 

21-25    .. 

9  3 

26-end    

11.6 

1907- 


1908- 


-March  had  3  days  with  1  hour  or  less  of  daily  sunshine. 
March  had  7  days  with  2  hours  or  less  of  daily  sunshine. 
April  had  6  days  with  1  hour  or  less  of  daily  sunshine. 
April  had  15  days  with  6  hours  or  less  of  daily  sunshine. 
May  had  2  days  with  1  hour  or  less  of  daily  sunshine. 
May      had    9  days  with  6  hours  or  less  of  daily  sunshine. 


-March  had  1  day 
March  had  3  days 
April     had  0  day 
April     had  2  days 
April    had  2  days 
May      had  0  day 
May      had  2  days 


with  1  hour  or  less  of  daily  sunshine. 
with  2  hours  or  less  of  daily  sunshine, 
with  1  hour  or  less  of  daily  sunshine, 
with  2  hours  or  less  of  daily  sunshine, 
with  6  hours  or  less  of  daily  sunshine, 
with  1  hour  or  less  of  daily  sunshine, 
with  6  hours  or  less  of  daily  sunshine. 


Average  amount  of  possible  daily  hours  of  sunshine  in  California 
for  March  is  about  12  hours ;  for  April,  13.5  hours ;  for  May,  14  hours. 
For  April,  1907,  there  was  52  per  cent  of  the  possible  amount  of  sun- 
shine ;  for  April,  1908,  there  was  78  per  cent ;  for  May,  1907,  there  was 
65  per  cent  of  the  possible  amount  of  sunshine;  for  May,  1908,  there 
was  74  per  cent  of  the  total  number  of  hours. 

X on-blighting  of  Late  Blooming  Trees. — As  previously  stated  in  the 
comparison  of  the  two  seasons,  the  season  that  opened  late,  that  is  1908, 
had  almost  no  walnut  blight.  What  was  true  of  the  majority  of  bear- 
ing trees  during  that  season  is  always  true  of  trees  that  bloom  late.  The 
majority  of  the  bearing  orchards  of  California  are  at  this  time  seedling 
trees,  differing  greatly  in  their  blooming  periods.  The  difference  in 
time  is  frequently  from  one  to  two  months  and  may  be  as  much  as  three 
months  between  the  earliest  and  the  latest  French  varieties.  Such  a 
wide  range  in  time  of  blooming  gives  considerable  chance  for  difference 
in  climatic  conditions.  We  find  that  the  early  or  medium  blooming 
trees  are  in  blossom  at  a  favorable  period  for  the  blight  to  develop 
while  the  late  bloomers  come  into  flower  at  a  time  when  bacteriosis  can 
make  little  headway.  Particular  attention  has  been  given  to  this 
phase  of  our  investigation  in  the  hope  of  finding  a  commercially  profit- 
able tree  that  blooms  at  a  season  when  conditions  for  the  infection  of 
the  small  nuts  is  at  a  minimum.     While  this  work  is  not  yet  completed 


342 


UNIVERSITY   OF    CALIFORNIA EXPERIMENT   STATION. 


enough  has  been  done  to  show  that  nuts  in  such  late  trees  are  compara- 
tively free  from  the  disease.  Some  of  these  late  varieties  are  described 
in  another  part  of  this  bulletin. 

Immunity. — Certain  trees  are  some  times  spoken  of  as  being  immune 
to  the  blight,  but  while  there  is  probably  no  such  thing  among  walnuts 
as  absolute  freedom  from  this  disease,  where  conditions  are  favorable 
for  blight  infection,  yet  some  trees  do  show  quite  a  marked  resistance, 
and,  if  otherwise  desirable,  are  given  precedence  in  new  plantings  on 
this  account.  (See  Eureka,  etc.)  It  may  be  that  in  certain  localities 
there  is  no  blight,  but  this  probably  is  not  due  to  any  immunity  that 
the  trees  possess  but  is  rather  the  effect  of  climatic  conditions  or  due  to 
the  fact  that  the  specific  organism  has  not  yet  reached  this  particular 
locality. 

Isolation. — Pure  cultures  of  the  walnut  bacteriosis  are  most  easily 
obtained  from  recently  diseased  nuts,  although  they  have  also  been 
secured  from  diseased  leaves,  old  lesions  and  young  blighted  shoots,  as 
well  as  from  certain  flies  that  are  quite  abundant  about  walnut  trees 
during  the  period  of  infection. 

Table  shoiving  dates  and  results  from  various  attempts  to  isolate  the  walnut  blight 
organisms  from  diseased  tissue. 


1907. 


Diseased  tissue. 


Number 

of  isola  - 

tions. 


Diseased  tissue. 


Number 
:  of  isola- 
tions. 


Oct.    25 


Nov.    5 


Dec.     3 


12 

19 

26 

1908. 

Jan.    7 


16 


30 


Pith   

Wood  and  bark.. 
Wood  and  pith- 
Bark   

Inside  hull 

Pith  

Wood  and  bark_. 

Green  hull 

Dry  meat 

Bark    

Wood  and  bark.. 

Pith  

Wood 

Bark    

Leaf   petiole   

Portion  hull 

Healthy  bark  __. 
Bark  and  wood.. 
Healthy  bark  __. 
Blackened  shell  _. 
Wood  and  bark- 
Wood  and  bark. 
Wood  and  bark- 
Wood  and  bark. 

Wood    

Nut  on  tree 

Wood  and  bark- 
Wood  and  pith.. 
Wood  and  bark 
Nut  from  tree- 
Totals  


+ 

mmm 

0 

1 

Feb.  4 

1 

0 

0 

1 

1 

0 

13 

0 

2 

4 

0 

19 

3 

0 

0 

1 

Mar.  2 

0 

2 

12 

1 

0 

16 

3 

0 

24 

1 

0 

30 

1 

0 

2 

0 

0 

1 

0 

1 

Apr.  3 

0 

1 

1 

2 

8 

0 

1 

0 

1 

4 

3 

14 

2 

2 

17 

0 

8 

21 

2 

8 

0 

2 

1 

0 

4 

0 

0 

2 

2 

2 

0 

1 

33 

42 

Wood  and  bark 

Wood    

Nut  from  tree 

Five  nuts  

Wood  and  bark 

Wood  and  bark 

Wood    

Wood  and  bark 

Wood  and  bark 

Wood  and  bark 

New  growth 

Pith   

Nut  

Wood    

Wood  and  bark 

Wood   

Wood  and  bark 

Young  nuts  

Young   shoots  

Petiole    

Small  nuts  

Blackened  leaves 

White  substances  on  surface 
of  lesion  

Totals  


23       24 


Bulletin-    231]  WALNUT    CULTURE   IN    CALIFORNIA.  343 

The  usual  method  of  securing  pure  cultures  was  as  follows:  A 
scalpel  sterilized  by  flaming  was  used  to  remove  the  outer  blight  portion 
of  the  young  nut.  Then  some  of  the  diseased  interior  of  the  nut  was 
transferred  to  liquid  media,  such  as  acid  Dunham  solution  or  acid 
peptone  meat  bouillon.  About  twenty-four  hours  after  inoculation 
there  is  usually  some  evidence  of  growth  and  dilution  cultures  were 
then  made  in  nutrient  agar.  In  two  to  five  days  at  a  temperature  of 
20°  C.  the  colonies  will  appear  and  can  then  be  transferred  to  potato 
cylinders  or  other  solid  media.  The  organisms  are  usually  abundant 
enough  in  the  diseased  nuts  to  plate  out  directly  from  the  diseased 
tissue  without  incubation. 

The  preceding  table  shows  that  the  organism  was  alive  at  all  seasons 
of  the  year  in  the  different  diseased  tissues.  The  number  of  isolations 
was  not  at  any  time  very  great,  but  sufficient  to  show  a  large  number 
of  positive  results.  The  negative  results  obtained  do  not  mean  there 
was  lack  of  growth  in  the  tubes  inoculated  with  the  diseased  tissue,  but 
that  there  was  usually  some  other  sort  of  bacterial  growth.  There  are 
several  kinds  of  saprophytic  organisms  that  can  be  found  in  these  old 
lesions.  In  the  dilution  cultures  a  saprophytic  yellow  organism  was 
very  often  present  and  could  not  always  be  distinguished  in  color  or 
manner  of  growth  from  that  of  the  walnut  bacteriosis.  The  difference 
in  growth  on  potato  cylinders,  however,  readily  distinguish  the  two. 
Even  when  lack  of  growth  did  occur,  too  much  importance  should  not 
be  placed  upon  it,  for  the  walnut  blight  organism  grows  more  slowly 
than  do  the  saprophytic  organisms  and  could  readily  be  crowded  out 
by  them  in  artificial  cultures. 


A  MORE  TECHNICAL  STUDY  OE  THE  WALNUT  ORGANISM. 

Pseudomonas  juglandis  Pierce. 
MORPHOLOGY. 
These  characteristics  were  studied  in  bouillon,  agar  and  potato  cul- 
tures from  twenty-four  to  forty-eight  hours'  growth,  except  in  old 
cultures  that  have  been  examined  for  spores. 

Form. — The  organism  has  rounded  ends  and  occurs  as  single  rods  or 
often  in  pairs,  and  more  rarely  in  chains  of  several  individuals,  com- 
monly four  to  eight. 

Size. — The  rods  as  found  in  diseased  tissue  and  stained  with  carbol- 
fuchsin  measure  1.5  to  3.01  microns  in  length  by  0.3  to  0.51  microns  in 
width. 

Staining  Reactions. — The  organism  stains  readily  with  the  usual  bac- 
teriological stains,  carbol-fuchsin,  aniline  gentian  violet,  aqueous  solu- 
tion of  methylene  blue,  gentian  violet,  and  by  Gram's  method.  Nothing 
especially  characteristic  was  observed  from  the  use  of  the  various  stains. 


344 


UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 


Spores. — No  spores  from  this  organism  have  thus  far  been  demon- 
strated. Old  cultures  have  many  times  been  studied  and  special  stains 
used.  Hauser  's  method  was  used,  but  did  not  show  anything  suggestive 
of  spores. 

Capsule.— The  organism  has  never  showed  a  true  capsule,  although 
its  viscid  growth  might  suggest  one,  and  a  microscopic  examination  of 
this  viscid  growth  from  potato  cylinders  and  other  culture  media  often 
shows  a  very  distinct  and  rather  thick  wall,  that  can  easily  be  seen  by 
using  some  of  the  special  stains  recommended  for  capsules.  This  may 
appear  as  a  hyaline  membrane  from  one  fourth  to  one  half  as  thick  as 
the  remaining  width  of  the  organism.  The  following  capsule  stains  were 
used :  Robberts '  dahlia,  Welch 's  and  Bonis '. 


Fig.  87. — 1,  the  walnut  blight  organism,  Pseudomonas 
juglandis,  greatly  enlarged ;  2,  a  mass  of  the  bacteria 
in    diseased   walnut   tissue. 

Flagella. — The  organism  is  motile  by  means  of  a  long,  single  polar 
flagellum,  as  may  be  demonstrated  by  using  Bowhill's  method.  The 
movement  of  the  organism  is  a  slow,  sinuous  one  in  the  direction  of  the 
longer  axis. 


CULTURAL  CHARACTERISTICS. 

The  culture  media  were  carefully  prepared,  following  directions  as 
given  by  Smith1  and  Moore.2  The  formula  for  preparing  nutrient 
bouillon  was  Witte's  peptone  10  grams;  (c.p.)  sodium  chloride  5  grams; 
500  grams  of  finely  minced  beef  to  1,000  c.c.  of  once-distilled  water.  In 
making  this  the  directions  given  by  Moore  were  followed. 


aBacteria  in  Relation  to  Plant  Diseases. 

laboratory  Directions  for  Beginners  in  Bacteriology. 


Bulletin    231]  WALNUT    CULTURE    IN    CALIFORNIA.  345 

Agar  Plates  (Surface  Colonies). — In  beef  peptone  acid  agar,  plus  15 
Fuller's  scale,  temperature  17°  to  18°  C,  the  colonies  became  visible 
after  forty-eight  hours  as  minute  whitish  specks  that  changed  with 
growth  to  straw  color  (stramineus),*  and  at  length  to  a  lemon  yellow. 
After  five  days'  growth  at  18°  C,  the  surface  colonies  measured  1.5  to 
2.5  mm.  in  diameter.  At  this  time  they  are  straw  color  (stramineus),* 
and  appear  raised  to  the  eye,  especially  at  the  center,  where  they  are  a 
deeper  yellow  color,  or  nucleated.  This  nucleated  character  of  the 
colony  is  quite  constant,  being  observed  even  in  quite  small  colonies. 
The  colonies  are  nucleated,  circular,  moist,  shining,  pale  yellow  with 
regular  margins.  When  examined  with  the  low  magnifying  power  of 
the  compound  microscope  the  margins  are  coarsely  granular,  while  the 
center  has  a  finer  and  denser  granular  structure.  Under  the  low  power 
magnification  the  colony  is  seen  to  have  several  concentric  zones  which 
probably  represent  different  regions  of  growth.  The  margins  are  entire 
or  slightly  undulatory.  After  twelve  days'  growth  the  colonies  have 
become  5  to  10  mm.  in  diameter  and  are  still  zoned  when  examined 
microscopically.  The  center  of  the  colony  (nucleus)  is  a  pale  lemon 
color,  while  the  margin  is  of  a  still  paler  yellow. 

Deep  Colonies. — These  colonies  are  at  first  white,  but  later  become 
lemon  color.  They  vary  somewhat  in  shape,  being  biconvex,  angular,  or 
oval  to  circular  in  outline. 

Agar  Slant. — On  acid  meat  peptone  agar  after  twenty-four  hours 
incubation  at  18°  C.  there  appears  a  slight  whitish  growth  along  the 
streak  and  on  the  adjacent  surface  of  medium.  In  five  days  there  is  a 
fairly  abundant  growth  spreading  on  either  side  of  the  streak.  Growth 
shining,  pale  lemon-yellow  (W.  and  N.)t  with  wavy  margins.  In  ten 
days  growth  covers  entire  surface  of  medium  and  often  shows  small 
colonies  at  side  of  main  growth.  In  the  older  tubes  there  sometimes 
appears  a  whitening  of  the  agar  just  beyond  the  line  of  growth.  This 
same  characteristic  was  also  observed  on  litmus  lactose  agar,  as  well  as 
on  stab  cultures  of  both  of  the  agars.  This  characteristic,  however,  is 
not  a  constant  one,  and  was  only  observed  a  very  few  times. 

Agar  Stab. — On  acid  meat  peptone  agar  after  twenty-four  hours  at 
18°  C.  growth  takes  place  along  the  line  of  puncture  and  on  the  sur- 
face of  medium  around  the  puncture.  Growth  on  surface  piled  up, 
yellowish.  The  growth  along  puncture  tuberculate-echinulate  (Ches- 
ter's terminology). 

Carbohydrate  Agars. — The  organism  was  grown  in  5  per  cent  dex- 
trose, lactose  and  glycerine  agar.     Shake  cultures  were  made  in  each 


*Chromotaxia  seu  Nomenclator  colorum — P.  A.  Saccardo. 

fWinsor  and  Newton's  specimen  tints  of  oil  and  water  colors.     Plate  5. 


346  UNIVERSITY   OP    CALIFORNIA EXPERIMENT   STATION. 

of  the  above  agars,  as  well  as  in  plum  agar.  In  three  days  at  24°  C. 
there  was  fine  growth  at  surface  of  medium  in  each  case,  but  no  growth 
deep  in  medium  in  tubes  and  no  indication,  at  any  time,  of  gas  forma- 
tion.    The  walnut  organism  seems  to  be  a  strict  aerobe. 

Litums  Agars. — The  walnut  organism  was  also  grown  on  litmus  lac- 
tose, litmus  galactose,  litmus  dextrose  media  and  litmus  saccharose. 
This  was  made  up  as  follows:  Distilled  water,  2  per  cent  Witte's  pep- 
tone, 0.5  per  cent  (c.  p.)  sodium  chloride,  2 \  per  cent  agar,  and  2 
per  cent  of  the  above-named  sugars;  titration  was  plus  12  Fuller's 
scale.  In  three  days  at  23°  C.  there  was  abundant  growth  along  the 
line  of  puncture  and  over  surface.  The  cultures  in  galactose  after 
seventy  days  showed  slight  reddening  of  the  agar  near  the  bottom  of  the 
tube,  but  not  nearly  so  decided  a  reaction  as  was  secured  with  the  olive 
organism,  Pseudomonas  olece  (Arc.)  Trev.  In  the  litums  dextrose  and 
litmus  lactose  there  was  no  visible  change  in  color  of  medium,  even  after 
two  months'  growth. 

Gelatin. — Ten  per  cent  gelatin  and  beef  peptone  bouillon  was  used. 
After  twenty-four  hours  at  20°  C.  there  was  a  slight  yellowish  growth 
along  the  line  of  puncture.  Liquefaction  begins  within  a  short  time  at 
the  surface.  The  type  of  liquefaction  is  crateriform  (Chester's  termi- 
nology) ,  the  liquefaction  being  at  first  restricted  to  the  mouth  of  the  stab 
and  forming  a  deep  pit.  As  growth  continues  the  liquefaction  extends 
laterally,  and  in  about  five  days  the  upper  portion  of  the  gelatin  in  the 
test  has  become  liquefied  and  would  be  termed  stratiform.  However, 
after  a  layer  of  liquefied  gelatin  has  formed,  further  liquefaction  at 
17°  C.  is  very  slow  and  does  not  take  place  at  all  along  the  line  of 
puncture.  It  often  requires  a  month  for  the  10  c.c.  of  gelatin  in  the 
test  tube  to  be  entirely  liquefied. 

Potato. — Growth  abundant,  moist,  shining,  slimy,  raised  and  piled 
up,  forming  a  thick  coating  that  in  about  two  months  becomes  viscid, 
finally  filling  up  the  fluid  with  a  yellow,  slimy  growth.  Color  of  the 
growth  on  potato  cylinders  was  at  first  white,  changing  in  a  few  days 
at  18°  C.  to  sulphureous  (Sacc.  Chrom.),  and  in  about  six  days  to 
a  pale  lemon  yellow  (W.  and  N.).  At  the  end  of  a  month  the  color  fre- 
quently became  citron  yellow  (W.  and  N.,  plate  No.  5).  In  cultures 
two  months  old  the  color  changed  to  raw  umber  shade  (W.  and  N.) 

The  growth  on  sterilized  potato  is  very  characteristic  because  of 
the  white  fermentation  band,  that  appears  just  beyond  the  margin  of 
growth.  This  can  be  observed  on  potato  cylinders,  or  better  still  on 
slices  of  potato  sterilized  in  petri  dishes.  The  white  zone  usually  is 
visible  within  three  days  from  inoculation  when  the  organism  is  grow- 
ing at  a  temperature  of  20°  C.  to  26°  C.     In  a  few  days  the  ferment  a- 


Bulletin   231] 


WALNUT    CULTURE   IN    CALIFORNIA. 


347 


tion  band  spreads  over  the  entire  surface  of  the  potato  slices.  The 
starch  where  growth  has  taken  place  fails  to  give  normal  starch  reac- 
tion when  treated  with  iodine,  but  gives  a  reaction  for  grape  sugar. 
This  fermentation  band  is  quite  a  constant  characteristic  and  usually 
appears.  When  the  organism  is  growing  slowly  and  at  a  rather  low 
temperature,  the  fermentation  band  is  more  likely  not  to  show. 

The  organism  lives  for  several  months  on  potato  cylinders,  having 
been  found  alive  at  the  end  of  four  months  when  growing  at  a  temper- 
ature of  15°  to  18°  C.  In  some  cases  the  cultures  die  after  three 
months.  In  the  old  tubes  the  cultures  are  very  viscid  and  much  darker 
in  color,  raw  umber.      ( W.  and  N.) 


Fig.   SS. 


-Typical    growth    of   Pseudomonas    juglandii 

on  potato. 


left   in   glucose   bouillon,    right 


Fermentation  Zone. — Special  attention  was  given  to  the  study  of  this 
fermentation  zone.  Early  in  the  study  it  was  found  that  this  was  a 
varying  characteristic,  one  that  appeared  constantly  during  the  warm 
weather  of  the  spring  and  summer,  but  failed  to  appear  during  the 
cooler  winter  weather.  This  point  was  tested  experimentally  by  ster- 
ilizing two  series  of  five  petri  dishes,  each  containing  slices  of  potato 
heated  at  110°  C.  in  autoclave  for  fifteen  minutes.  These  two  series  of 
five  plates  each  were  inoculated  at  the  same  time  and  from  the  same 
culture.  Both  series  of  cultures  grew  well.  Series  I  at  a  temperature 
of  12°  to  15°  C.  This  we  did  not  vary  for  five  days  from  15°  C. 
Growth  was  as  vigorous  as  in  those  at  the  higher  temperature.     No 


348  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

fermentation  zone  was  observed  during  the  fourteen  days  of  the  exper- 
iment. 

In  the  incubator  at  23°  to  26°  C.  growth  began  to  show  after  twenty- 
four  hours.  In  forty-eight  hours  on  December  16,  1908,  the  growth 
had  increased  and  was  very  vigorous  and  the  fermentation  zone  was 
just  beginning  to  appear  in  all  of  the  five  cultures  as  a  very  faint, 
whitish  line  outside  the  margin  of  growth.  This  zone  constantly  became 
more  evident,  and  on  the  fourth  day  from  inoculation  was  at  its  best. 
Further  growth  was  slower  and  no  great  change  was  to  be  observed 
during  the  two  weeks  of  observation. 

Professor  Pierce  in  his  study  laid  stress  upon  this  characteristic  to 
separate  the  walnut  organism  from  the  closely  related  species,  Pseu- 
domonas  campestris.  To  test  this,  we  secured  a  culture  of  the  latter 
organism  from  Dr.  H.  A.  Harding  of  the  Geneva  Experiment  Station 
of  New  York  State.  On  July  1,  1911,  potato  slices  were  inoculated  in  the 
same  way  as  has  already  been  described.  Black  rot  of  cabbage  (Pseudo- 
monas  campestris)  and  walnut  organisms  were  used.  July  5th,  the  two 
series  of  cultures  were  examined.  Both  cultures  from  the  incubator  at 
26°  to  28°  C.  showed  fine  fermentation  zone  formation.  In  fact,  it  would 
be  difficult  to  distinguish  one  from  the  other.  The  culture  of  the  walnut 
organism  grown  in  the  culture  room  at  a  temperature  of  20°  C.  showed 
very  good  fermentation  zone  formation,  while  that  of  Pseudomonas 
campestris  was  much  less  developed.  Dr.  H.  A.  Harding,  in  his  study 
of  this  organism,  speaks  or  a  "white  margin  or  halo  just  outside  of  the 
line  of  growth."* 

Other  Solid  Media. — The  organism  was  also  grown  on  slices  of  sweet 
potato,  turnip,  garden  beet  and  carrot,  Irish  potato  being  used  as  a 
check.  Slices  of  these  vegetables  were  sterilized  for  fifteen  minutes  in 
the  autoclave  at  110°  C,  then  inoculated  from  the  same  source  and 
grown  in  the  incubator  at  23°  to  26°  C.  for  several  days.  After  six 
days  there  was  abundant  growth  on  each  of  the  different  vegetables, 
but  nothing  characteristic  on  any  of  these  media  except  that  of  the 
Irish  potato  where  the  white  fermentation  zone  appeared,  as  has  been 
before  described. 

Bouillon. — On  meat  peptone  bouillon,  plus  15  Fuller's  scale,  the 
organism  grows  well,  and  in  forty-eight  hours  at  18°  C.  the  liquid  is 
uniformly  turbid.  In  seven  days  there  is  a  slight  flocculent  precipi- 
tate at  the  bottom  of  tube.  A  true  pellicle  has  never  been  observed 
to  form  over  the  surface  of  this  medium,  but  a  ring-like  growth 
develops  readily  at  margin  of  liquid  on  the  surface  of  test  tube. 


*New  York  Agricultural  Experiment  Station,  Geneva,  Technical  Bulletin  No.  13. 


Bulletin    231]  WALNUT    CULTURE   IN    CALIFORNIA.  349 

Dunham  Solution. — The  growth  in  this  medium  shows  very  much  the 
same  characteristics  as  in  bouillon.  In  cultures  over  a  week  old  the 
liquid  is  clouded. 

Carbohydrates  in  Bouillon. — The  walnut  organism  was  grown  in  the 
following  bouillons,  containing,  respectively,  2  per  cent  glucose,  dex- 
trose, lactose  and  glycerine  saccharose.  These  solutions  were  made  up 
by  adding  the  carbohydrate  to  a  solution  of  meat  peptone,  solution  made 
after  the  formula:  1  per  cent  Witte's  peptone,  0.5  per  cent  sodium 
chloride,  0.5  per  cent  Liebig's  meat  extract.  These  solutions  titrated 
plus  12  Fuller's  scale.  Growth  took  place  within  forty-eight  hours, 
and  at  the  end  of  five  days  fine  growth  showed  in  all  the  tubes  of 
this  series.  The  glucose  series  of  tubes  showed  a  well  developed  ring 
formation,  while  in  the  other  media  there  were  traces  of  ring  formation, 
but  much  less  than  in  glucose.  There  was  no  complete  pellicle  observed 
in  these  tubes.     They  were  titrated,  but  showed  no  increase  of  acid. 

Cohn  Solution. — Formula  as  given  by  E.  F.  Smith  was  used.*  Five 
lubes  were  inoculated  with  forty-eight-hour  culture  of  walnut  organism, 
but  after  three  months  there  was  no  growth  in  tubes. 

Milk. — The  cream  was  removed  from  milk  that  had  set  over  night  in 
an  ice  box.  The  same  was  filtered  and  sterilized  in  steam  sterilizer. 
Reaction  was  plus  10  to  15  Fuller's  scale.  These  tubes  were  inoculated 
and  grown  at  temperatures  25°  to  27°  C.  In  three  days  the  separation 
of  the  casein  was  first  observed.  The  coagulum  is  formed  rather  slowly 
and  even  after  five  days  there  is  little  separation  of  the  whey,  and  no 
pellicle  to  be  seen  at  this  time.  The  curd  and  whey  gradually  separate 
from  each  other,  the  former  becoming  solid.  The  casein  is  soon  acted 
upon  by  another  enzyme  and  is  gradually  redissolved,  probably  by  a 
trypsin  ferment.  This  process  of  digestion  takes  place  usually  rather 
slowly,  several  months  often  being  required  for  completion.  After  a 
month  the  white  curd  may  be  observed  at  the  bottom  of  the  tube 
while  the  liquid  above  is  of  a  yellowish  color  (yellowish  straw  color).! 
At  first  the  whey  is  clear  and  nearly  colorless,  but  changes  to  a  yellowish 
color,  as  stated  above,  when  reabsorption  of  the  casein  has  taken  place. 
Upon  a  microscopic  examination  of  the  liquid  directly  above  the  casein 
that  is  in  process  of  reabsorption  many  crystals  can  be  seen.  The  most 
conspicuous  of  these  are  long,  needle-like  crystals.  A  pellicle  at  length 
forms  on  the  surface  of  the  liquid  in  the  milk  tubes. 

Litmus  Milk. — The  characteristics  are  very  much  like  those  just  given 
for  milk.  Separation  of  casein  takes  place  by  a  rennet  ferment,  or 
rarely  digestion  occurs  without  casein  separation ;  the  tubes  under  these 


♦Bacteria  in  Relation  to  Plant  Diseases. 
tRepertoire  de  Couleurs,  Henri  Dauthenay. 


350  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

conditions  have  a  wine-colored  liquid.  Litmus  was  slowly  changed  so 
as  to  give  a  pinkish  or  wine-colored  appearance  to  liquid,  sometimes 
eifter  one  to  two  months. 

Methylene  Blue  Milk. — This  medium  was  made  by  adding  2  per  cent 
aqueous  solution  of  methylene  blue  (Merck)  to  milk  and  sterilizing 
same.  In  one  to  two  days  at  19°  to  20°  C.  the  color  completely  dis- 
appeared and  could  be  restored  by  boiling  or  shaking  the  liquid  in  the 
tube  a  few  minutes.  The  disappearance  of  color  seems  to  take  place 
first  at  the  lower  part  of  tube.  The  color  entirely  disappears  some  time 
before  separation  of  casein  can  be  detected. 

Plant  Juices. — The  walnut  organism  grows  well  in  plant  juices. 
While  no  great  number  has  been  tested,  the  following  extracts  gave 
abundant  growth:  Leaves  of  walnut  {Juglans  regia),  loquat,  castor 
bean  and  fig.  A  ring  formation  and  pellicle  as  well  as  a  flocculent 
precipitate  are  produced  in  these  media. 

Viability  in  Media. — In  order  to  test  the  period  of  viability,  transfers 
were  made  to  potato  cylinders  from  milk  culture  at  the  end  of  five, 
seven  and  eight  months.  Growth  resulted  in  several  cases.  Old  potato 
cylinders  were  also  tested.  All  these  cultures  were  growing  in  dark 
at  a  temperature  from  15°  to  20°  C. 

From  potato  cultures  made  December  10,  1910,  transfers  were  made 
on  September  28,  1911,  a  period  of  about  nine  and  one  half  months. 
On  October  4,  1911,  there  was  growth  in  one  of  the  two  tubes  tested, 
the  other  showing  fungus  growth.  These  old  potato  cultures  just 
referred  to  seemed  to  be  thoroughly  dried  out,  hard,  and  for  the  most 
part  brittle.  When  placed  in  the  liquid  of  the  potato  cylinder  tube 
the  old,  dried-out  portion  absorbed  water,  becoming  swollen  and  more 
like  its  former  viscid  condition.  Another  potato  culture  six  and  one 
half  months  old  also  produced  fine  growth  when  transferred  to  sterile 
potato  cylinders.  In  these  cases  of  old  potato  cultures  it  is  perhaps  more 
an  instance  of  resistance  to  desiccation,  also  possibly  this  resistance  may 
be  due  to  spore  formation,  although  these  have  never  thus  far  been 
demonstrated. 

Indol. — This  reaction  was  tested  in  Dunham  solution  made  as  fol- 
lows: Witte's  peptone  1  per  cent,  sodium  chloride  0.5  per  cent,  and 
distilled  water.  After  two  weeks,  the  cultures  were  tested  for  indol 
with  sodium  nitrate  0.02  per  cent  and  a  few  drops  of  concentrated 
sulphuric  acid.  The  tubes  after  treatment  did  not  at  once  show  the 
characteristic  pink  reaction,  but  when  warmed  for  five  minutes  at  75° 
to  80°  C.  in  a  hot  water  bath,  a  strong  indol  reaction  resulted,  the  color 
being  deep  cherry  red. 

Nitrate  Reduction. — A  meat-peptone  medium  was  used  that  titrated 
plus  12  Fuller's  scale.     It  was  made  after  this  formula:  1  per  cent 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  351 

Witte's  peptone,  0.5  per  cent  sodium  chloride,  0.5  per  cent  Liebig's 
meat  extract,  0.5  per  cent  potassium  nitrate  (Merck).  Good  growth 
took  place  in  these  tubes  after  five  days  at  25°  to  27°  C.  They  were 
tested  by  the  KI  H2S04  starch  method  as  recommended  by  E.  F.  Smith.* 
Not  the  slightest  nitrate  formation  was  shown  in  any  of  the  tests. 

Enzymes. — The  walnut  organism  produces  at  least  four  enzymes, 
diastatic  (starch-destroying),  cytohydrolytic  (cellulose-dissolving),  ren- 
net (casein-forming),  proteolytic  (peptonizing).  Professor  Pierce 
statesf  in  his  article  on  this  disease  that  he  found  that  these  enzymes 
are  especially  active  at  a  temperature  between  65°  to  75°  F.,  and  this 
agrees  very  well  with  our  study  of  growth  of  the  organism  on  potato 
slices  and  the  accompanying  fermentation  zone. 

Attention  was  called  by  Professor  Pierce  to  the  marked  similarity 
between  the  organisms  of  walnut  bacteriosis  and  the  black  rot  of  the 
cabbage.  While  few  comparative  studies  have  been  made,  yet  the 
cultural  characteristics  of  the  two  are  very  similar  indeed.  The  few 
cross-inoculations  made  with  Pseudomonas  campestris  on  walnut  and 
Pseudomonas  juglandis  on  cabbage  show  that  the  pathogenic  proper- 
ties are  distinct.  The  walnut  organism  also  grows  more  readily  on 
plant  juices. 

The  group  number  of  the  organism,  in  accordance  with  the  system 
prepared  by  the  American  Society  of  Bacteriologists,  is  211.3332513. 
It  will  be  observed  that  this  is  identical  with  that  of  Pseudomonas 
campestris. 

ARTIFICIAL  INOCULATIONS. 

Methods. — Inoculations  have  been  successfully  made  at  various  seasons 
of  the  year  and  in  two  different  ways,  by  puncture  and  by  atomizing. 
The  puncture  method  is  the  most  likely  to  give  positive  results.  A  steri- 
lized needle  is  used  to  transfer  some  of  the  germs  from  a  pure  culture 
into  a  wound  made  by  a  slight  pricking  of  the  surface.  The  atomizing 
method  was  used  also  quite  effectively  on  the  young  nuts,  but  gave  no 
results  on  foliage  or  the  young  shoots.  A  young  pure  culture  of  the 
walnut  blight  organism  grown  on  potato  for  about  three  days  was  mixed 
with  distilled  water  and  the  mixture  sprayed  on  the  nuts  or  shoots  with 
an  ordinary  medical  atomizer,  without  injuring  the  tissue.  This  experi- 
mental work  has  extended  over  two  seasons.  The  season  of  1907  was 
one  favorable  for  blight  development  from  natural  infections,  while  that 
of  1908  produced  very  little  walnut  blight.  The  time  and  results  from 
atomizing  during  1907  and  1908  are  given  in  tables  which  follow. 

Atomizing  on  Late  Tree. — The  results  summarized  in  the  following 


♦Bacteria  in  Relation  to  Plant  Diseases. 

fBailey's  Encyclopedia  of  American  Horticulture,  p.   1961. 


352 


UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION. 


table  represent  work  done  by  spraying  healthy  nuts  with  a  water  solu- 
tion of  the  organism  on  a  rather  late  blooming  tree,  being  in  blossom 
from  the  middle  to  the  last  of  April.     The  nuts  were  always  very  free 


Fig.   S9. — Below- 


-Stigma  exudation  from  blighted  nuts, 
infected  with  Bacteriosis. 


Above — Nuts  artificially 


from  blight,  and  when  the  atomizing  work  was  begun  no  blight  of  any 
kind  could  be  found  on  this  tree  nor  did  it  ever  develop  to  any  extent  at 
other  points  than  those  that  were  atomized. 


Bulletin   231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


353 


Atomizing  results  on  nuts   of   late   blooming   tree  with  water  solution  of  the  walnut 
blight   organism    from    pure  cultures,  at  different  periods. 


1007. 


Nuts 
atomized. 


Diseased 
nuts. 


Healthy 
nuts. 


Date  of 
observation. 


April  27  . 
April  29  _ 
May  2  ... 
May  16  . 
May  20  . 
June  8  _. 
June  26  _ 
June  27  . 
Juno  29  . 
July  2  ... 
July  3  ... 
July  6  ... 
July  7  ... 
July  9  ... 
July  13  _. 

Totals 


May 
June 
June 
June 
June 
June 
July 
July 
July 
July 
July 


August  13 
August  1 
August  1 
August  14 


352 


214 


74 


The  table  shows  that  a  total  of  352  nuts  were  atomized  at  the  different 
dates  and  that  244  or  about  69  per  cent  of  those  treated  contracted  the 
disease.  Thirty-five  of  the  treated  nuts  dropped  before  final  results 
were  obtained  and  were  not  counted  in  the  results,  although  the  chances 
are  that  a  large  number  of  these  were  also  diseased  and  would  still 
farther  have  increased  the  percentage  of  diseased  nuts. 

Table  showing  results  from  atomizing  nuts  on  an  early-blooming  tree. 


SB 

O^ 

Observation. 

Experi- 
ment. 

~3 

5  6             Nuts 

f>  "■    i     atomized. 

p 

eg 

1      01 

i    a> 
!    & 

ll 

i  a 

GO  — 

ll 

i 

i 
i 

3g 

:  s 
■  & 

ST  CD 

i   s 

oo- 

H 

P 
1 

1     

?    

3    

i    

5    

i 
i 
l 

i 

l 
l 
l 

i 

2 
2 

I 

10 
14 
14 
14 
17 
17 
17 
17 
21 
21 
21 
28 
28 

431 
431 
431 
431 
431 
203 
203 
203 
203 
203 
203 
203 
203 

7 

7 

8 
21 
punctured 

6 
10 

7 

punctured 
23 

9 
13 
punctured 

11 
11 
11 
11 

14 
14 
14 

14 
14 

8 

17 
25 
25 
21 
25 
25 
25 

25 

25 

25 
5-5 
5-5 

0 
0 
0 
0 

branch 
0 
0 
0 

branch 
0 
0 
0 

branch 
1 
0 
1 
0 
0 
0 
2 
twig 
0 
0 
4 
0 
0 

8 

0 
0 
0 
0 

17 
17 
17 
17 

2 
3 
5 
7 

0 

1 

1 

2 

21 

21 

21 

21 

21 

25 

21 

25 

21 

25 

25 

25 

25 

25 
5-20 
5-20 
5-2 
5-20 

2 
3 

7 
13 

positive 

! 

positive 
5 
0 

positive 
5 

• 

4 
4 
2 


0 
3 

1 
4 

20 

2 

2 

20 

3 

1 
0 
0 

7    

8    

9 

0 

0 
0 

0 

0 
0 

0 
4 
7 
0 
0 
9 
4 

21 
17 
17 

3 
2 

1 

1 
1 
2 

3 
3 
2 

20 
20 
20 

1 

0 

1 

10    

11    

12    

i:;   

17 
21 
21 

21 
5-2 
5-2 
4-25 
5-2 
5-2 
5-5 

0 

0 

2 

2 
0 
3 
1 
2 
5 
6 

4 
3 
0 

0 
6 
7 
4 
0 
12 
6 

10 

5 
3 

20 

20 
20 

1 

2 
10 

25   

33    

34    

35    

36    

37  .. 

220     10 
444       8 
444      11 
297  i  10 
462        5 
462      19 
462      12 
462     punctured 

3 

1 
7 
4 
1 

25 

20 
20 
20 
20 

0 
1 
0 
2 
3 

38    



20 

0 

39    

4-25 
5-20 
5-20 
5-20 

positive 
7 
4 
5 

50    

51    

53    

64    

462 

462 

462 

462 

2 

13  large 
12  large 
22 

6 

8 

2 

o 

4 
1 
0 

31 

5-2 

5-2 

5-2 

5-20 

5-20 

0 
0 
1 
4 
2 

51 

2 

6 

14 

1 

1 

74 

5 

8 
15 

20 
20 
20 

10 
20 

--! 

1 
0 
2 
1 

65    

5-20 

2 

1 

5 

Totals.- 

247 

70 

79 

34 

Atomizing  on  Early  Tree. — The  preceding  table  shows  the  results 
from  inoculation  by  atomizing  of  small  nuts  on  a  very  early  blooming 
16—231 


354 


UNIVERSITY    OP    CALIFORNIA EXPERIMENT    STATION. 


tree.  The  season  of  blooming  for  1908  was  about  three  weeks  later  than 
that  of  1907.  During  the  period  that  this  experiment  was  taking  place 
there  was  no  natural  infection  developing  on  the  nuts  of  this  tree  or  in 
the  orchard.  The  climatic  conditions  were  decidedly  unfavorable  for 
blight  development.  From  these  inoculations  a  fair  percentage  of  the 
nuts  became  diseased,  while  from  those  that  dropped  no  accurate  data 
was  secured. 

It  should  be  remembered  that  the  season  of  1908  was  one  in  which  the 
nuts  were  practically  free  from  blight,  and  yet  from  our  atomizing 
experiments  the  blight  could  be  produced  when  the  germs  were  placed 
on  the  nuts,  although  the  percentage  was  somewhat  less  than  that  of 
1907,  because  of  the  less  favorable  conditions.  The  small  amount  of 
blight  for  1908  was  due  largely  to  a  lack  of  foggy  weather,  which  is  one 
of  the  chief  ways  in  which  the  germs  are  distributed  to  the  nuts  from  the 
old  natural  sources  of  infection  on  the  branches. 


Table  showing  source  of  culture  and  tests  of  puncture  inoculation  on  young  shoots. 


eg- 
|    o 

Date 
of  isola- 
tion. 

Source  of 
isolation. 

Date 

puncture 
inocu- 
lations. 

Eesults. 

Date 
of  obser- 
vation. 

Remarks. 

13 

06 
1-  3-07 

1-  3-07 

2-  6-07 
2-  6-07 
2-  9-07 
2-22-07 
2-27-07 
2-27-07 
3-14-07 
3-27-07 
3-27-07 
3-27-07 
4-  2-07 
5-17-07 

5-17-07 
10-25-07 
10-25-07 

11-  5-07 
11-16-07 
11-16-07 
11-16-07 

12-  3-07 
12-12-07 
12-12-07 
12-19-07 
12-19-07 

1-  7-08 
1-16-08 

2-  4-08 

2-  4-08 
2-19-08 
2-19-08 

3-  3-08 
3-12-08 

4-  3-08 
4-3-08 
4-  8-08 
4-14-08 
4-17-08 

Unknown  

4-  2-08  !  Positive 
2-22-08  ;  Positive 
2-22-08      Positive 

4-  4-08 
4-24-07 
4-24-07 
5-10-07 
4-25-08 
5-30-07 
5-30-07 
5-27-07 

5-  9-07 
5-  9-07 
5-  9-07 
5-  9-07 
4-11-08 
5-16-07 

Cultured  two   years. 
Cultured  one  year. 

Year-old  culture. 

Positive   atomizing   experi- 
ments . 

Fine  results. 

Fine  results. 

Isolation    from    puncture 
oculation  97A. 

Fine  results. 

33  C 

Pith    

36  C 

Pith    .     __ 

86B 
92A 

Wood  and  bark— 
Bark 

3-19-07 
4-  2-08 
3-27-07 
4-11-07 
4-24-07 
4-  2-07 
4-16-07 
4-16-07 
4-16-07 
4-  1-08 
4-27-07 

Positive 
Positive 
Positive 
Positive 
Positive 
Positive 
Positive 
Positive 
Positive 
Positive 
Positive 

97A 

Wood 

133B 
144A 
145A 

Inner  bark 

Wood  and  bark___ 
Wood 

186A 
202B 
203B 
203B 

220A 
289A 

New  growth 

Small  nuts 

Small  nuts 

Small  nuts 

Small  nuts — 

White     substance 

on    surface    of 

lesion. 

290A 

6-  8-07 
4-  2-08 
4-  2-08 
5-11-08 
4-  2-08 
4-  2-08 

4-  2-08 

5-  5-08 
5-20-08 
5-  5-08 
5-  5-08 
5-  5-08 
5-  5-08 
5-20-08 
5-20-08 
5-20-08 

4-  1-08 
5-20-08 

5-20-08 
4-14-08 
5-11-08 

5-  5-08 
4-17-08 
5-  6-08 
5-  6-08 

Positive 

Positive 

Positive 

Doubtful 

Positive 

Positive 

Positive 

Positive 

Positive 

Positive 

Positive 

Positive 

Positive 

Positive 

Positive 

Positive 

Positive 

Positive 

Positive 
Positive 
Positive 
Positive 
Positive 
Positive 
Positive 

6-19-07 
4-25-08 
4-25-08 
6-  1-08 
4-11-08 
4-11-08 
4-11-08 
6-  1-08 
6-  1-08 
6-  1-08 
6-  1-08 
6-  1-08 
6-  1-08 
6-  1-08 
6-  1-08 
6-  1-08 
4-17-08 
6-  1-08 

6-1-08 
5-20-08 
6-20-08 
6-1-08 
4-25-08 
5-20-08 
6-  1-08 

323A 
325B 

Wood  and  bark___ 
Bark 

335A 

Pith 

344B 

Bark    

347A 

Wood 

348B 
363A 
366B 
367A 
371B 
3720 
399B 
403C 
417A 

Wood  and  bark- 
Wood  and  bark___ 
Wood  and  bark— 
Wood  and  bark- 
Wood  and  bark___ 
Wood  and  bark___ 

Nut  on  tree 

Wood  and  bark___ 
Wood               

421X 
431X 
435A 

440B 
444A 
460B 

Nut  on  tree 

Wood  and  bark- 
Wood  and  bark- 
Wood  and  bark- 
Wood      

in- 

Bark 

461A 
462A 
465 
467 

Wood  and  bark- 

New  leaves 

Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  355 

Puncture  Inoculation. — The  puncture  experiments  shown  in  the  pre- 
ceding table  were  on  young  growing  shoots  with  culture  from  potato 
cylinders  after  three  to  five  days'  growth.  These  experiments  give 
almost  uniformly  positive  results.  During  the  past  two  seasons  many 
such  inoculations  were  made  and  a  few  of  these  are  summarized  in  the 
preceding  table.  Many  other  cultures  of  yellow  organisms  that  some- 
what resemble  the  walnut  blight  growth  were  also  tested,  but  with  nega- 
tive results.  The  table  shows,  furthermore,  that  cultures  isolated  from 
pith,  wood,  bark,  nuts  and  leaves  all  produced  the  typical  blight  lesions. 
In  several  instances  cultures  that  had  been  grown  on  artificial  media  one 
and  two  years  gave  positive  results  from  puncture  inoculations. 

MORE    DETAILED    ACCOUNT   OF    INOCULATION    EXPERIMENTS. 

The  following  description  gives  more  detail  regarding  certain  of  the 
more  suggestive  experiments : 

1.  Puncturing  of  Nuts. — April  2,  1907,  seven  young  nuts  were  inocu- 
lated by  puncture  with  a  sterilized  needle  carrying  germs  from  a  pure 
culture  of  walnut  blight.  April  12th  five  of  the  nuts  were  still  attached, 
and  all  showed  infection  at  every  place  where  punctured. 

2.  Contact  Inoculation. — April  2,  1907,  six  small  nuts  were  inculated 
by  simply  placing  the  sticky  bacterial  growth  from  a  pure  potato  culture 
in  contact  with  the  nuts  without  making  a  puncture  of  any  kind.  April 
12th  four  of  the  nuts  were  still  attached  and  showed  positive  infection 
at  points  of  inoculation. 

3.  Atomizing  Nuts. — From  culture  isolated  about  six  months  previ- 
ously and  cultivated  during  the  meantime  in  artificial  media.  April  12, 
1907,  5  p.  m.,  eight  small  nuts  were  atomized  with  culture  from  potato, 
eight  days'  growth.  The  day  had  been  cloudy  most  of  the  time  and 
was  still  cloudy  when  the  experiment  was  made.  April  30th  six  nuts 
were  attached,  three  of  them  healthy  and  three  diseased  at  one  or  two 
points.  May  9th  six  nuts  were  attached  and  four  of  them  had  one  or 
two  points  of  infection.  A  shoot  inoculated  at  the  same  time  by  punc- 
ture showed  positive  infection. 

4.  Atomizing  nuts  from  culture  of  blight  isolated  from  diseased  new 
growth. — April  16,  1907,  six  small  nuts  were  atomized  with  six  days' 
growth  of  organism  on  potato  cylinders.  This  culture  was  originally 
isolated  from  blight  on  new  growth.  May  9,  1907,  the  six  nuts  were 
still  attached  and  showed  fine  positive  results  with  many  points  of 
infection.  Is  the  use  of  a  culture  recently  made  from  blight  on  new 
growth  the  cause  of  so  fine  positive  results  ? 

5.  Atomizing  nut  by  using  solution  of  water  and  diseased  tissue. — 
April  27,  1907,  six  small  nuts  on  a  late  blossoming  tree  were  atomized 


356 


UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION. 


by  using  a  solution  of  water  and  diseased  nuts.  May  21st  six  nuts  were 
attached  and  four  of  these  were  diseased,  each  on  one  to  four  places. 
Other  nuts  on  the  tree  were  free  from  blight. 

6.  Atomizing  at  Various  Hours  of  the  Day. — June  8,  1907,  small  nuts 
were  atomized  at  different  periods,  9  to  10  a.  m.,  5  to  6  p.  m.  The 
results  are  tabulated  in  the  following  table : 


June  8, 

Number 

Results 

Results 

Results 

1907. 

ized. 

June  14. 

June  19. 

June  24. 

Remarks. 

+         — 

+         — 

+         — 

9:03  a.m. 

6  nuts 

0          6 

6         0 

9:10 

7  nuts 

1          5 

3          3 

6         0 

1  nut  dropped. 

9:25 

5  nuts 

0          5 

1          5 

5          0 

9:35 

12  nuts 

5         0 

7  nuts  dropped. 

9:56 

7  nuts 

1          6 

__ 

7         0 

4:20  p.m. 

10  nuts 

0        10 

5          5 

10         0 

4:25 

5  nuts 

0          5 

0          5 

4          0 

1  nut  dropped. 

4:35 

5  nuts 

__ 

2          3 

4          1 

5:20 

4  nuts 

0          4 

0          4 

4          0 

5:35 

9  nuts 

0          8 

0          8 

8         0 

1  nut  dropped. 

5:50 

6  nuts 

0         6 

1          5 

6          0 

Totals- 

76  nuts 

2        49 

12        44 

65          1 

10  nuts  dropped. 

The  results  from  experiment  6  show  no  difference  in  the  infecting 
power  of  the  organism  for  the  different  hours  of  the  day.  The  day  was 
bright,  sunny  and  warm.  Another  interesting  fact  was  that  the  orchard 
was  being  irrigated  at  the  time  the  atomizing  inoculations  were  made. 
The  ground  continued  to  be  wet  for  about  a  week  after  the  experiment 
was  made,  and  the  results  were  exceptionally  fine,  as  all  the  inoculations 
showed  many  points  of  infection.  The  nuts  treated,  with  hardly  an  ex- 
ception, were  all  badly  blighted  with  hundreds  of  points  of  infection. 
The  extreme  virulence  of  the  infections  are  probably  because  of  favor- 
able external  conditions,  due  without  doubt  to  the  additional  moisture 
in  the  air  from  the  evaporation  of  the  irrigation  water.  On  this  tree, 
as  well  as  on  trees  in  orchard  not  treated,  no  additional  development  of 
blight  occurred,  and  it  is  not  probable  that  irrigation  in  any  way  in- 
creases the  amount  of  blight  in  an  orchard,  as  at  the  time  walnut 
orchards  are  irrigated  the  conditions  necessary  for  carrying  the  germs 
from  the  sources  of  infection  are  usually  lacking.  From  our  field  obser- 
vations we  have  never  associated  in  any  way  an  increase  of  blight  with 
orchard  irrigation. 

7.  July  2  and  3,  1907. — Atomized  twenty-six  nuts  of  different  sizes, 
as  follows:  5  nuts  1J  inch  diameter,  13  nuts  1J  inch  diameter,  8  nuts 
If  inch  diameter.  The  weather  at  this  time  was  very  bright  and  hot,  as 
it  was  for  several  days  following.  The  temperature  was  about  100°  F. 
during  the  middle  of  the  day.  The  atomizing  was,  however,  done  be- 
tween 5  and  5 :30  p.  m.,  when  it  was  somewhat  cooler.  The  results  on 
July  16th  showed  5  of  the  If  inch  diameter  nuts  to  be  negative  and  3 


Bulletin   231] 


WALNUT    CULTURE   IN    CALIFORNIA. 


357 


positive,  10  of  the  1J  inch  diameter  nuts  negative  and  3  positive,  and 
3  of  the  1^  inch  diameter  nuts  negative  and  2  positive.  August  1st, 
however,  showed  all  of  the  26  nuts  to  be  more  or  less  diseased.  The 
smaller  nuts  were  covered  with  many  different  points  of  infection,  while 
the  larger  nuts  had  a  much  smaller  number  of  diseased  places,  usually 
about  twelve  on  each. 

8.  The  following  table  shows  that  there  was  very  slight  infection  in 
the  afternoon,  when  the  sun  was  shining  brightly  and  the  spray  from 
the  atomizer  evaporated  rapidly.  The  influence  of  the  bright  sunlight 
would  also  kill  many  of  the  organisms  in  the  liquid  atomized  on  the  nuts. 
The  nuts  that  were  infected  from  the  afternoon  atomizing  had  very  few 
places  of  infection  as  compared  with  those  of  the  early  forenoon.  The 
atomizing  in  the  early  forenoon  produced  a  large  number  of  infections 
one  month  after  inoculation;  those  atomized  in  the  afternoon  showed  a 
very  small  percentage  of  infection  as  well  as  few  points  of  infection : 


Results 

Results 

Number 

July  23. 

August  14. 

July  13, 

atom- 
ized. 

Infection  points  on  each  nut. 

1907. 

Positive. 

Negative. 

Positive,    t  Negative. 

7:20  a.m. 

8  nuts 

0 

7 

6 

0 

10  to  50. 

7:30 

3  nuts 

0 

3 

0 

3 

Negative  results. 

7:35 

3  nuts 

0 

3 

3 

0 

7:45 

10  nuts 

0 

10 

10 

0 

5  to  100. 

7:50 

2  nuts 

0 

2 

1 

1 

Diseased  at   | 

8:00 

15  nuts 

1 

14 

5 

10 

10  to  20.         > 

3:00p.m. 

4  nuts 

0 

5 

1 

2 

1  spot. 

3:20 

4  nuts 

0 

4 

1 

3 

1  spot. 

3:25 

5  nuts 

0 

5 

1 

4 

3  spots. 

3:30 

3  nuts 

0 

3 

0 

3 

3:40 

7  nuts 

0 

7 

0 

7 

INOCULATIONS  ON  OTHER  SPECIES  OF  JUGLANS. 

Puncture  inoculations  were  tried  on  the  several  species  of  Juglans  that 
were  available.  These  trees  were  not  of  an  age  to  produce  nuts,  so  little 
atomizing  was  done.  Experiments  were  made  on  the  eastern  black, 
Juglans  nigra;  on  the  northern  California  black,  Juglans  hindsii;  on  the 
southern  California  black,  Juglans  calif ornica;  on  butternut,  Juglans 
cinerea;  on  Japanese  walnuts,  Juglans  cordiformis  and  sieboldiana.  Be- 
sides these  experiments,  others  were  made  on  several  hybrids.  Paradox 
hybrid,  a  cross  between  the  English  and  the  California  black  walnut ;  the 
Royal  hybrid,  a  cross  between  the  eastern  and  California  black. 

Eastern  Black. — These  were  seedlings  that  had  grown  two  years  in  our 
nursery  from  Iowa  black  walnuts.  Last  season's  growth  had  been  cut 
off  in  grafting  and  vigorous-growing  sprouts  had  come  up  from  the  roots. 
Inoculations  were  from  pure  cultures  on  these  vigorous-growing  sprouts. 
No  difficulty  was  found  in  producing  the  typical  disease  lesions. 


358  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

Northern  California  Black. — These  were  seedling  trees  growing  in  our 
station  nursery.  Vigorous,  fast-growing  sprouts  from  roots  that  had 
been  grafted  were  inoculated  by  puncture  and  gave  definite  positive 
results.  One  observation  is  worthy  of  mention.  In  a  single  case  the 
walnut  bacteriosis  was  observed  to  have  spread  from  one  of  the  positive 
puncture  inoculations  to  the  nearby  leaves  of  the  tree.  On  these  leaves 
typical  black  spots  appeared  on  the  soft  tissue  of  the  leaf,  as  well  as  on 
the  veins,  which  were  blackened.  The  black  areas  of  the  leaf  appeared 
to  be  quite  characteristic  and  somewhat  different  from  the  effect  on  the 
English  walnut,  in  that  the  black,  diseased  and  partially  dried-out 
tissue  was  surrounded  by  a  narrow,  yellowish-green  zone  just  between 
the  dried-out  and  healthy  tissue.  Artificial  cultures  were  made  by 
plating  out  directly  from  the  diseased  tissue  and  gave  yellow  colonies 
which  produced  the  characteristic  growth  on  potato  cylinders. 

Southern  California  Black. — A  single  tree  about  five  years  old  was 
first  used  in  this  experiment  work.  Nuts  were  atomized  in  the  same  way 
as  with  English  walnuts  and  gave  positive  results.  May  11,  1909,  nine 
nuts  were  atomized  with  a  water  solution  of  the  walnut  organism  that 
had  grown  on  potato  for  six  days.  May  18,  1909,  three  nuts  showed 
positive  infection  and  six  negative.  Later  observations  did  not  show 
further  infection  on  the  other  atomized  nuts.  Puncture  inoculations  on 
nuts  and  shoots  were  also  made.  The  punctured  nuts  often  gave  positive 
results,  but  inoculations  on  the  shoots  of  this  tree  gave  negative  results. 
This  may  be  accounted  for  because  of  the  woody,  hard  growth.  Later 
puncture  experiments  on  young  southern  California  black  seedlings  gave 
fine  positive  results  and  there  can  be  no  doubt  as  to  the  organism  being 
able  to  infect  the  southern  variety. 

Butternut. — Puncture  experiment  on  a  two-year-old  seedling  gave  fine 
positive  results. 

Japanese  Walnut. — J.  cordiformis  and  J.  sieboldiana  were  inoculated 
by  puncture,  but  gave  rather  uncertain  results.  Positive  inoculations 
were  produced  in  a  few  cases,  but  usually  the  lesion  formed  did  not 
appear  typical,  being  simply  a  depressed,  blackish  spot  without  the  usual 
water-soaked  zone  surrounding  the  puncture.  These  later  healed  up 
readily  and  would  seem  to  show  negative  results.  Results  on  these  two 
species  are  not  as  conclusive  as  could  be  desired,  but  we  believe  that  on 
young,  vigorous,  succulent  growth  infection  could  be  produced. 

Hybrids. — Fine  positive  puncture  inoculations  were  produced  on  the 
Royal  Hybrid,  the  Paradox  and  Strong  Hybrid  (a  local  Paradox 
Hybrid).  These  hybrids  are  vigorous  in  growth  and  the  disease 
develops  fully  as  well  as  on  either  of  the  blacks  or  the  English  walnut. 

Walnut  blight  was  found  during  the  spring  of  1909  on  the  nuts  of  a 


Bulletin   231] 


WALNUT    CULTURE    IN    CALIFORNIA. 


359 


Paradox  Hybrid  and  typical  cultures  were  obtained  from  the  diseased 
nuts.  Probably  all  species  of  Juglans  can  be  made  to  take  the  disease, 
although  it  has  not  been  found  in  nature  on  either  the  eastern  or  Cali- 
fornia black.  Even  the  black  seedlings  in  the  nursery,  where  the  dis- 
ease usually  appears,  are  free  from  the  trouble.  Blight  infection  occurs 
not  uncommonly  on  hybrids. 

Pecan  seedlings  were  also  inoculated  very  thoroughly  to  see  if  it 
would  be  possible  to  produce  the  blight  by  using  pure  cultures  of  the 
walnut  organism.     Only  negative  results  were  obtained. 

Desiccation. — Several  experiments  were  made  to  test  out  the  effect  of 
drying  or  desiccation  on  the  walnut  organism. 

Methods. — The  general  method  of  testing  out  the  resistance  of  the 
organism  was  as  follows : 

First  a  tube  of  Dunham  solution  or  other  liquid  medium  was  inocu- 
lated from  a  pure  culture  and  after  a  faint  cloudiness,  was  visible  usually 
after  twenty-four  hours,  a  loopful  of  this  growth  was  placed  on  half  inch 
cover  glasses  that  had  been  sterilized  in  a  petri  dish.  These  were  kept 
in  darkness  and  tested  out  by  dropping  them  in  tubes  of  sterilized  liquid 
media  and  if  growth  took  place,  dilution  plates  were  poured  and  trans- 
fers made  from  them  to  potato  cylinders.  If  the  characteristic,  vigor- 
ous, piled-up,  yellow  growth  occurs  here  there  is  little  doubt  of  its  being 
that  of  the  walnut  bacteriosis.  In  some  of  the  last  of  our  desiccation 
work  it  was  found  to  be  necessary  to  make  dilution  cultures  from  the 
tubes  which  had  been  inoculated  with  the  desiccated  cover  glasses,  in 
order  to  be  positive  that  the  growth  was  due  to  that  of  the  walnut  blight 
organism.  In  this  work  transfers  were  made  directly  to  potato  cylinders 
from  these  inoculated  tubes.  The  growth  on  potato  is  the  most  con- 
clusive single  test  by  which  to  identify  this  organism. 

Experiment  I. — November  5,  1908,  3  p.  m.  Sterile  cover  glasses  were 
inoculated  with  a  two-millimeter  loopful  of  a  22-hour  culture  made  by 
inoculating  a  tube  of  Dunham  solution.  These  cover  glasses  were  kept 
m  darkness  at  20°  C.  and  tested  out  as  indicated  in  the  following  table : 


Time  of  desiccation. 


Number 

tubes. 


Date  of 

inoculation 

media. 


Date  of 
planting. 


Result. 


Date  of 
observa- 
tion. 


1  day  9 

2  days   8 

3  days   9 

4  days   9 

6  days   9 

8   days 10 


11-  6^08 

11-  9-08 

11-  7-08 

11-10-08 

11-  8-08 

11-10-08 

11-  9-08 

11-13-08 

11-11-08 

11-18-08 

11-13-08 

11-18-08 

8  tubes  show  blight 
7  tubes  show  blight 

0  tubes  show  blight 

1  tube  shows  blight 
3  tubes  show  blight 
3  tubes  show  blight 


11-18-08 
11-18-08 
11-18-08 
11-30-08 
12-10-08 
12-15-08 


360 


UNIVERSITY   OP    CALIFORNIA — EXPERIMENT    STATION. 


Experiment  II. — Made  further  test  of  resistance  to  desiccation  on 
December  18,  1908,  under  similar  conditions  to  those  indicated  under 
Experiment  I.     The  following  table  shows  tabulated  results: 


Day  of  desic- 
cation. 

Number 
tubes. 

Date  of 
testing 
covers. 

Date  of 
planting. 

Number  with 
growth. 

Number  with 
walnut  blight. 

Date  of 
obser- 
vation. 

3  days   

5  days  

7  days  

8  days  

10  days  

12  days  

20  days  

29  days  

10 
14 
17 
10 
13 
20 
14 
13 

12-21-08 
12-23-08 
12-25-08 
12-26-08 
12-28-08 
12-30-08 
1-  7-09 
1-16-09 

12-26-08 

12-30-08 

12-31-08 

12-31-08 

1-  4-09 

1-  4-09 

1-12-09 

1-20-09 

2  tubes  with  growth 

2  tubes  with  growth 

3  tubes  with  growth 
1  tube   with  growth 

1  tube   with  growth 

2  tubes  with  growth 

4  tubes  with  growth 

3  tubes  with  growth 

2  show  blight 
2  show  blight 
1  show  blight 
1  show  blight 
1  show  blight 
1  show  blight 
4  show  blight 
0  show  blight 

1-12-09 
1-12-09 
1-12-09 
1-12-09 
1-12-09 
1-12-09 
1-21-09 
1-15-09 

The  experiment  showed  very  few  tubes  with  the  blight  organism  alive 
even  after  three  days,  but  some  of  the  tubes  show  growth  of  the  organism 
even  after  twenty  days. 

Experiment  777.— January  2,  1911.  Used  a  three-day-old  culture 
growing  in  a  meat  peptone  glucose  bouillon  made  as  follows:  5  gm. 
Liebig  meat  extract,  5  gm.  NaCl,  10  gm.  Witte's  peptone,  1,000  c.c. 
distilled  water,  5  gm.  glucose  (Merck).  This  same  medium  was  also 
used  in  which  to  test  the  desiccated  cover  glasses.  A  loopful  of  culture 
was  placed  on  each  sterilized  one  half  inch  cover  glass,  using  a  2  mm. 
loop  on  the  platinum  needle.  These  covers  were  dropped  into  the  above 
medium  at  given  intervals  of  time,  as  is  shown  in  the  following  table : 


Date  of  inoculation. 

Number 
tubes. 

Number  days 
desiccation. 

Results. 

January  1,  1911          _______      

5 
10 
10 
10 
10 
10 
11 
10 
10 

3  days 
7  days 
10  days 
15  days 
18  days 
23  days 
39  days 
57  days 
73  days 

4  tubes  with  walnut  bacteriosis 

January  9,  1911 

January  12,  1911             _                   _ 

5  tubes  with  walnut  bacteriosis 

January  17,  1911        _          _               __  _ 

January  20,  1911          .       _          - 

January  25,  1911 

February  10,  1911      __          .  _        

8  tubes  with  walnut  bacteriosis 

March  1,    1911     

March  16,  1911  _    _  _ 

The  inoculated  tubes  were  incubated  at  20°  to  25°  C,  as  well  as  the 
inoculated  potato  cylinders.  The  desiccating  cover  glasses  were  kept  at 
about  15°  C.  This  organism  belongs  to  a  genus  in  which  are  several 
yellow  chromogenic  organisms  that  are  quite  resistant  to  drying. 

Experiment  TV. — This  experiment  was  a  combination  of  desiccation 
and  influence  of  light.  March  9,  1908,  a  tube  of  Dunham  solution  was 
inoculated.  After  three  days'  growth  at  20°  C.  this  liquid  was  atomized 
on  living  olive  shoots  about  one  year  old. 

Series  1.     The  same  liquid  was  atomized  on  a  small  English  walnut 


Bulletin    231] 


WALNUT    CULTURE   IN    CALIFORNIA. 


361 


tree  one  year  old  that  had  been  cut  off.     The  bark,  however,  was  still 
green  and  had  not  dried  out  at  the  time  of  the  experiment. 

Series  2.  Pieces  of  the  atomized  bark  were  then  cut  out  from  time 
to  time  and  dropped  into  the  test  tubes  of  nutrient  media,  in  the  same 
way  that  cover  glasses  were  used  in  the  other  desiccation  experiments. 

Series  I. 


.'   day  . 

2  days 

4  days 

17  days 


Series  II. 


Number  clays  drying. 

Number  tubes. 

Positive. 

Negative. 

1  day           .                       _________________ 

3 
3 
3 
3 
3 

2 
1 
1 
2 
0 

1 
2 
2 
1 
3 

2  days                                   -  __ . 

3  days                      _  _                                      - 

1  days        __________                            _               __  _ 

1/  days                                                     ______ 

Growths  in  the  inoculated  tubes  were  plated  out  and  transfers  of 
yellow  colonies  were  made  to  potato  cylinders.  The  characteristic 
growth  on  this  medium  was  taken  to  be  conclusive  evidence  that  the 
growth  was  that  of  the  walnut  bacteriosis  organism. 


ACTION   OF  GERMICIDES  ON   THE   WALNUT  ORGANISM. 

Considerable  work  has  been  done  in  experimenting  upon  the  effective- 
ness of  various  germicides  in  killing  the  walnut  organism.  Copper 
sulphate,  mercuric  chloride,  formalin,  potassium  permanganate  and 
sodium  benzoate  were  used  in  this  work. 

Method. — The  following  method  was  employed  in  testing  the  killing 
of  organism : 

A  pure  culture  of  the  walnut  blight  organism  was  grown  for  twenty 
to  forty-eight  hours  in  Dunham  solution.  The  culture  tubes  at  this  time 
were  considerably  clouded  with  growth.  Then  three  loopfuls  of  the 
culture  were  transferred  with  a  2  mm.  loop  to  tubes  containing  the 
germicide  under  experimentation.  The  germicide  was  always  made  up 
with  distilled  water  and  of  several  different  strengths.  In  each  tube 
there  was  a  definite  amount  of  the  germicide,  either  5  or  10  c.c.  In  all 
cases,  except  formalin,  the  tubes  were  sterilized  on  three  successive  days 
for  twenty  minutes. 

Copper  Sulphate.— In  this  experiment  the  commercial  copper  sulphate 
was  used  with  distilled  water.  The  following  strengths  were  tested : 
1/10  per  cent,  1/100  per  cent,  1/500  per  cent,  1/1000  per  cent, 
1/2500  per  cent.  1/5000  per  cent. 


362  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

Each  of  the  tubes  to  be  tested  had  5  c.c.  of  the  copper  sulphate  solu- 
tion and  was  sterilized  on  three  successive  days.  There  were  three 
tubes  of  each  of  the  preceding  dilutions  as  well  as  three  check  tubes 
of  distilled  water.  Each  of  the  tubes  was  inoculated  with  three  loopfuls 
of  a  walnut  blight  culture  grown  in  Dunham  solution  for  forty-eight 
hours.  The  loop  of  needle  was  2  mm.  in  diameter.  Three  hours  after 
being  inoculated  dilution  plates  were  made  from  each  of  the  tubes  under 
experiment  by  transferring  three  loopfuls  of  the  inoculated  germicidal 
tube  to  meat  peptone  agar.  These  plates  constituted  series  I  of  the 
experiment.  After  six  hours  from  inoculation  of  tubes  containing  the 
germicide  a  second  plating  out  from  the  tubes  was  made  in  the  same 
manner  as  the  first. 

The  results  after  seven  days'  growth  in  the  Petri  plates  showed  that 
no  growth  resulted  in  the  plates  of  series  I  made  from  1/100  per  cent, 
1/500  per  cent,  1/1000  per  cent  or  1/2500  per  cent  copper  sulphate. 
In  the  check  tubes  as  well  as  in  the  1/5000  per  cent,  a  large  number  of 
colonies  developed. 

The  three  plates  made  from  the  1/5000  per  cent  had  8,  30  and  60 
walnut  blight  colonies,  while  the  two  check  plates  had  200  and  225 
blight  colonies,  and  the  third  plate  had  a  spreading,  white,  foreign 
organism  that  covered  the  entire  surface  of  plate  and  covered  up  the 
walnut  blight  growth. 

In  series  II,  plated  out  after  six  hours'  incubation,  no  growth 
occurred  during  seven  days. 

Another  experiment  made  earlier  in  the  study  gave  almost  the  same 
results.  The  1/100  per  cent,  1/500  per  cent  and  1/1000  per  cent  killed 
the  organism,  while  the  1/5000  per  cent  failed  to  do  so.  No  test  was 
made  of  the  1/2500  per  cent  in  this  experiment.  The  per  cent  of 
copper  sulphate  sufficient  to  kill  is  somewhere  between  1/2500  and 
1/5000  per  cent. 

Mercuric  Bichloride  (corrosive  sublimate). — The  same  general 
method  was  employed  as  with  copper  sulphate.  Four  tubes  each  of 
the  following  strengths  were  used  in  distilled  water:  1/100  per  cent, 
1/500  per  cent,  1/1000  per  cent,  1/5000  per  cent,  and  1/10000  per 
cent  and  two  check  tubes  of  distilled  water.  All  were  sterilized  and 
then  inoculated  with  four  loopfuls  of  a  24-hour  growth  of  the  organism 
in  meat  bouillon.  In  four  hours  from  inoculation,  plates  were  made 
from  each  tube.  After  six  days'  time  no  growth  developed  in  any  but 
the  check  plates  and  these  showed  41,  48  and  150  colonies  each. 

Another  experiment  with  corrosive  sublimate,  using  more  dilute 
strength  in  distilled  water,  was  made.  Three  tubes  of  each  of  the 
following  strengths  were  tested:  1/1000  per  cent,  1/10000  per  cent, 
1/50000  per  cent,  1/100000  per  cent,  1/500000  per  cent,  and  1/1000000 


Bulletin-    231]  WALNUT    CULTURE   IN    CALIFORNIA.  363 

per  cent.  Dilution  plates  were  made  after  three  hours'  time,  using 
four  loopfuls  from  each  tube  to  inoculate  the  agar  tubes.  In  seven 
days  the  following  results  were  given:  Growth  in  1/10000  per  cent 
and  the  weaker  strengths. 

Carbolic  Acid. — The  following  per  cents  were  made,  using  distilled 
water  to  properly  dilute  the  5  per  cent  stock  solution  of  carbolic  acid 
Merck)  :  1/2, 1/4,  1/10,  1/25, 1/50,  1/100  per  cents,  four  tubes  of  each 
and  three  check  tubes  of  distilled  water.  Tubes  were  inoculated 
with  three  loopfuls  of  walnut  blight  culture  and  dilution  plates  were 
made  after  three  hours.  After  six  days  1/2  and  1/4  per  cents  showed 
either  no  growth  or  at  least  not  walnut  blight.  The  other  lower  per 
cents  1/10,  1/25,  1/50,  and  1/100  showed  some  growth.  The  1/10  per 
cent  developed  12  and  7  colonies  in  two  of  the  plates,  while  the  other 
two  showed  no  growth. 

An  attempt  w^s  at  first  made  to  use  the  carbolic  acid  with  a  solution 
containing  peptone,  but  the  results  are  not  exact  because  there  was  a 
precipitate  due  to  the  chemical  action  of  the  acid  with  the  peptone.  A 
series  of  tubes  containing  Dunham  solution  and  carbolic  acid  was  made 
and  the  tubes  inoculated  with  three  loopfuls  from  a  four  days'  growth 
in  meat  bouillon.  Growth  and  cloudiness  of  tubes  occurred  in  1/25, 
1/50  and  1/100  per  cents.  No  growth  in  tubes  having  1,  1/2,  and  1/4 
per  cents.  Plates  were  made  from  the  tubes  and  the  results  obtained 
agree  with  the  statements  above. 

Formalin. — A  1/25  per  cent  solution  acting  for  three  hours  on  the 
organism  was  effective  in  killing.  A  solution  of  1/50  per  cent  formalin 
acting  for  the  same  time  did  not  kill. 

Potassium  Permanganate — A  solution  of  1/500  per  cent  acting  for 
three  hours  killed  the  organism. 

Sodium  Benzoate. — This  chemical  was  tested  but  showed  poor  germi- 
cidal action.  A  solution  of  1  per  cent  did  not  kill  the  organism  even 
after  six  days'  time.  This  strength  was  sufficient  to  inhibit  growth  of 
organism  when  used  in  Dunham  solution,  but  when  plates  were  made 
from  these  tubes  colonies  of  walnut  blight  developed. 

CONTROL    OF   WALNUT   BLIGHT. 

Spraying. — The  earliest  attempts  at  the  control  of  this  disease  con- 
sisted, as  has  been  the  case  with  most  plant  diseases,  in  spraying  with 
Bordeaux  mixture.  Pierce  carried  on  a  considerable  amount  of  such 
work  and  at  his  suggestion  a  number  of  growers  gave  this  method  of 
treatment  quite  a  thorough  trial.  As  a  result  of  his  work  Pierce  recom- 
mended spraying  with  Bordeaux  mixture  just  before  the  trees  came 


364  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

into  leaf  in  the  spring,  and  also  a  later  spraying  during  the  early 
summer  if  the  latter  should  be  considered  necessary  or  practicable. 
He  likewise  urged  the  removal  of  all  affected  twigs  and  fruit  spurs. 
Professor  Pierce  stated  that  by  following  these  recommendations 
thoroughly  it  was  possible  to  reduce  the  number  of  blighted  nuts  by 
fifty  per  cent.  Mr.  E.  G.  Ware,  of  Garden  Grove,  while  in  charge  of 
a  large  walnut  grove  near  Placentia,  which  belonged  at  that  time  to 
Thum  Brothers,  carried  on  what  was  probably  the  most  extensive  and 
most  carefully  conducted  experiment  along  this  line.  For  several 
years  he  sprayed  thoroughly  with  Bordeaux  mixture,  using  large  blocks 
of  trees  and  leaving  unsprayed  trees  or  rows  as  checks.  Mr.  Ware 
came  to  practically  the  same  conclusion  as  Professor  Pierce,  namely, 
that  the  number  of  blighted  nuts  could  be  reduced  about  50  per  cent 
by  spraying  with  Bordeaux  mixture  just  as  the  buds  are  swelling. 
Neither  of  these  experimenters  was  able  to  state  any  distinct  increase 
in  the  crop  obtained  by  spraying,  but  it  should  be  said  that  such  a 
measure  of  results  is  practically  impossible  in  seedling  walnut  groves 
on  account  of  the  extreme  variation  in  the  production  of  the  various 
individual  trees.  Mr.  Ware  also  experimented  with  the  application 
of  lime  to  the  soil  after  Professor  Pierce's  suggestion,  with  the  idea 
that  this  might  produce  a  firmer,  harder  tissue  in  the  growth  of  the 
trees  and  thus  render  them  less  susceptible  to  blight.  He  believed 
that  some  benefit  was  derived  from  such  an  application,  using  large 
quantities  of  air-slacked  or  sugar-beet  factory  refuse  lime.  Other 
growers  have  sprayed  their  walnut  trees  with  Bordeaux  mixture  and 
various  other  materials  at  different  times,  but  it  may  be  said  in  a 
general  way  that  such  practice  has  never  become  common  and  for 
several  years  it  has  been  entirely  discontinued. 

At  the  commencement  of  this  work  in  1905  plans  were  made  to  carry 
on  very  thoroughly  and  systematic  spraying  experiments  in  order  to 
determine  definitely  the  extent  to  which  blight  control  could  be  accom- 
plished by  this  means.  In  the  spring  of  1906  several  large  blocks  of 
good  sized  seedling  walnut  trees  were  obtained  for  this  purpose  in  the 
vicinity  of  Whittier  and  spraying  operations  were  commenced.  The 
principal  experiments  were  made  with  three  different  fungicides, 
Bordeaux  mixture,  lime-sulphur,  and  a  sulphur  spray  made  by  boiling 
together  sulphur  and  caustic  potash.  The  work  was  done  with  a  power 
sprayer,  and  was  carried  on  more  thoroughly  and  carefully  than  any 
grower  would  be  likely  to  do  such  spraying  and  without  regard  to 
expense.  In  one  instance  a  large  block  of  trees  was  sprayed  with 
Bordeaux  mixture,  using  a  5-6-50  formula,  in  another  a  heavy  lime- 
sulphur  was  used,  the  spray  being  prepared  by  boiling,  while  in  the 
third  the  potash-sulphur  spray  mentioned   above  was   used.     It  was 


Bulletin    231]  WALNUT    CULTURE   IN    CALIFORNIA.  365 

found  in  all  this  work  that  to  spray  large  walnut  trees  thoroughly  is 
an  extremely  slow,  difficult,  and  expensive  operation.  In  the  case  of 
the  largest  trees  no  attempt  was  made  to  spray  more  than  two  thirds 
of  the  tree  from  the  bottom  up,  inasmuch  as  the  top  could  not  be 
thoroughly  covered  without  using  a  very  high  platform.  Our  experi- 
ence was  that  to  spray  a  good  sized  tree  thoroughly  or  to  cover  even 
two  thirds  of  an  extra  large  tree  required  at  least  twenty  gallons  of 
material.  We  found  further  that  with  the  outfit  used,  consisting  of 
three  men  to  spray  and  one  to  mix,  not  more  than  fifty  good  sized 
trees  could  be  sprayed  in  one  day,  while  with  the  largest  ones  thirty 
was  about  the  limit  of  a  day's  work.  It  was  found  further  that  even 
when  the  work  was  done  with  apparent  thoroughness  on  these  large 
trees  many  portions  of  the  top  remained  unsprayed  the  first  time 
over.  This  was  detected  particularly  in  spraying  with  lime-sulphur, 
where  the  sprayed  and  unsprayed  portions  of  the  tree  showed  up  in 
strong  contrast  as  soon  as  the  spray  had  dried.  For  this  reason  it  was 
found  necessary  with  these  large  trees  to  go  back  over  them  sometimes 
two  or  three  times  in  order  to  be  sure  that  every  twig  and  branch 
which  might  harbor  blight  lesions  was  covered  with  the  spray.  As 
regards  expense,  we  found  that  we  could  not  thoroughly  spray  good 
sized  trees  for  less  than  about  50  cents  each,  counting  labor  and 
materials,  while  with  many  of  the  largest  trees  the  outlay  amounted  to 
at  least  $1.00  per  tree  even  though  the  top  of  the  tree  was  not  sprayed 
at  all.  As  a  result  of  this  experience  we  were  led  very  soon  to  believe 
that  the  general  spraying  of  California  walnut  groves  for  blight  con- 
trol would  be  extremely  difficult  of  accomplishment  during  the  period 
of  time  available  for  such  work,  and  also  that  it  would  be  extremely 
difficult,  if  not  absolutely  impossible,  for  the  average  grower  to  get 
the  work  done  thoroughly  enough,  even  though  the  spraying  done  by 
ourselves  should  prove  extremely  effective  in  controlling  the  disease. 

During  the  summer  following  our  spraying  careful  observations 
were  made  from  time  to  time  of  the  condition  as  to  blight  of  the  sprayed 
and  unsprayed  trees  in  the  experimental  orchards.  From  such  obser- 
vations no  difference  whatever  in  the  prevalence  of  the  disease  on  the 
nuts  could  be  detected.  Many  of  the  sprayed  trees  lost  a  large  portion 
of  their  crop  from  blight,  and  even  on  individual,  rather  small  trees 
or  individual  branches  which  had  been  especially  well  sprayed  and 
absolutely  covered  with  the  mixture  much  blight  developed  on  the  nuts, 
and  it  soon  became  apparent  that  no  satisfactory  degree  of  control,  if 
any,  had  been  secured  by  our  work.  In  the  fall  weighings  were  made 
of  the  crop  from  the  various  trees  and  blocks,  but  owing  to  the  extreme 
variation  in  the  crop  of  individual  seedling  trees  the  result  was  the 
same  as  in  our  fertilizer  experiment  described  on  page  185,  namely  that 


366  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

no  conclusions  whatever  could  be  drawn.  This  much,  however,  was 
very  evident  from  observation,  that  a  very  large  amount  of  blight 
developed  on  many  of  the  sprayed  trees  and  that  no  decided  benefit  in 
the  season's  crop  of  nuts  had  been  obtained  by  the  spraying.  Even 
where  trees  or  branches  had  been  perfectly  and  entirely  coated  with 
heavy  lime-sulphur  solution,  a  large  number  of  blighted  nuts  appeared. 

As  a  result  of  our  experience  in  1906,  first  with  the  cost,  difficulty, 
and  slowness  of  spraying  large  walnut  trees,  and  second  with  the  lack 
of  effect  of  such  spraying,  we  became  thoroughly  convinced  that  the 
possibilities  of  walnut  blight  control  did  not  lie  in  this  direction. 
Furthermore,  as  the  prospect  of  obtaining  varieties  of  the  walnut  more 
or  less  immune  to  the  disease,  and  likewise  of  much  better  quality  and 
much  greater  production  than  the  average  seedlings,  became  brighter 
and  brighter  the  undesirability  of  spraying  methods  became  still  more 
pronounced.  For  these  reasons  no  further  extensive  spraying  experi- 
ments were  made  by  us  and  we  still  believe  that  the  ultimate  control  of 
walnut  blight  does  not  lie  in  this  direction.  It  should  be  stated,  how- 
ever, that  during  the  following  year,  that  is  in  1907,  the  appearance  of 
the  trees  sprayed  in  the  spring  of  1906  gave  some  reason  to  believe  that 
the  blight  was  less  prevalent  on  the  sprayed  than  on  the  unsprayed  trees. 
This  was  particularly  true  in  the  case  of  trees  sprayed  with  lime- 
sulphur.  It  is,  therefore,  not  improbable  that  while  infection  of  the 
nuts  during  the  year  when  the  spraying  was  done  was  not  prevented, 
that  the  twig  and  shoot  infection  was  somewhat  controlled  and  that  on 
this  account  less  blight  was  carried  over  winter  and  less  nut  infection 
took  place  the  following  year.  It  is  further  possible  and  quite  likely 
that  thorough  spraying  year  after  year  would  have  a  cumulative  effect 
and  might  eventually  reduce  the  amount  of  blight  to  a  noticeable  and 
satisfactory  extent.  Even  if  this  were  true,  however,  we  have  not  felt 
that  it  would  be  practical  to  accomplish  this  to  any  general  extent  on 
account  of  the  reasons  mentioned  above. 

During  the  past  season  or  two  there  has  been  a  considerable  revival  of 
interest  in  walnut  spraying  in  one  portion  of  the  State,  namely,  in 
Santa  Barbara  and  Ventura  counties.  This  has  been  due  to  the  impor- 
tance of  the  walnut  industry  in  that  region,  the  serious  prevalence  of 
blight,  and  to  the  fact  that  a  certain  proprietary  remedy  or  mixture  has 
received  considerable  prominence  in  that  locality  and  has  been  used  in 
a  large  part  of  the  spraying  which  has  been  done  there.  Walnut  spray- 
ing having  thus  become  somewhat  customary  in  the  counties  mentioned, 
some  work  has  been  done  there  with  Bordeaux  mixture  and  various  other 
materials  which  have  suggested  themselves  to  the  growers.  We  do  not 
wish  to  discourage  such  attempts  at  blight  control  in  a  region  where 
some  of  our  oldest  and  finest  seedling  groves  exist,  one  which  is  espe- 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  367 

cially  adapted  to  walnut  culture,  and  where  the  maintenance  of  the 
present  groves  is  of  as  much  or  perhaps  more  importance  than  the  possi- 
bilities of  planting  new  ones.  The  chief  problem  in  walnut  blight 
control  by  spraying  lies,  in  our  opinion,  not  so  much  in  the  discovery  of 
a  specific  for  the  disease,  since  there  is  no  reason  why  any  good  fungicide 
should  not  be  as  good  as  any  other  for  this  purpose,  but  rather  in  the 
development  of  means  of  spraying  these  large  trees  rapidly  and  econom- 
ically and  at  the  same  time  thoroughly.  Investigations  are  still  being 
continued  along  this  line,  particularly  in  cooperation  with  Mr.  C.  W. 
Beers,  horticultural  commissioner  of  Santa  Barbara  County,  and  a 
renewal  of  spray  work  along  new  lines  and  upon  a  considerable  scale  is 
being  prepared  for. 

Blight  Control  by  Means  of  Applications  to  the  Soil. — Various  sug- 
gestions and  experiments  have  been  made  along  the  line  of  applying 
various  substances  to  the  soil  with  the  idea  of  controlling  walnut  blight 
by  this  means.  Especially  prominent  has  been  the  application  of  lime, 
mostly  beet  factory  refuse.  It  is  impossible  to  state  definitely  just 
what  may  have  been  accomplished  by  such  methods  as  these,  but  it  is 
very  certain  that  nothing  of  this  sort  has  resulted  in  blight  control  to  an 
extent  at  all  significant  or  important.  In  trees  which  are  suffering  for 
plant  food  the  growth  may  be  stimulated  and  increased  by  heavy  appli- 
cations of  stable  manure  or  nitrogenous  fertilizers,  and  as  a  result  of 
this  the  crop  may  be  increased  and  the  loss  by  blight  lessened.  This  we 
believe  to  be  the  extent  of  any  good  results  which  may  be  obtained  by 
the  application  of  any  substance  to  the  soil. 

Resistant  Varieties. — It  has  been  noted  ever  since  walnut  blight  first 
became  prevalent  in  California  that  there  is  a  great  difference  in  indi- 
vidual trees  as  to  the  extent  to  which  they  are  affected  by  the  disease. 
Some  trees  regularly  lose  almost  all  their  nuts  by  blight,  others  are  no- 
ticeably free  from  it,  while  others  vary  from  year  to  year,  being  badly 
blighted  one  year  and  comparatively  free  from  the  disease  the  next.  As 
a  result  of  such  observations  the  possibility  of  selecting  or  producing 
blight  immune  varieties  was  suggested  several  years  ago.  Pierce  in  his 
work  considered  this  phase  of  the  matter,  and  brought  together  a  collec- 
tion of  walnut  species  and  varieties  from  various  parts  of  the  world,  as 
well  as  local  selections,  with  this  object.  On  account,  however,  of  the 
discontinuance  of  his  walnut  work  no  definite  results  along  this  line  have 
ever  been  announced  by  Professor  Pierce.  Various  nurserymen  have 
also  worked  to  some  extent  along  the  same  linej  endeavoring  to  pick 
out  and  propagate  from  individual  trees  of  uniformly  large  production 
of  nuts.  The  fact  was  early  established  that  the  extent  to  which  indi- 
vidual trees  blight  depends  with  much  regularity  upon  the  season  at 
which  the  trees  develop  in  the  spring,  trees  late  in  coming  out  being 


368  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION. 

freer  from  blight  than  those  which  open  their  buds  earlier  in  the 
season.  The  reason  for  this  difference  was  easily  apparent,  being  con- 
nected with  conditions  of  atmospheric  moisture.  Trees  coming  out  late 
escape  the  spring  rains  and  fogs,  which  period  is  by  far  the  worst  for 
blight  infection.  Some  observations  seem  to  indicate  that  trees  com- 
ing out  unusually  early  in  the  spring  are  also  freer  from  blight  than 
the  average,  and  there  appears  to  be  some  truth  in  this  fact.  If  this 
is  correct,  it  is  probable  that  these  early  trees  escape  blight  infection 
owing  to  the  lower  temperature  which  prevails  at  the  time  when  their 
shoots  and  nuts  are  young  and  easily  susceptible.  We  have  shown 
elsewhere  that  the  blight  organism  requires  a  fairly  high  temperature 
for  its  most  vigorous  development.  These  early  and  late  blight-free 
trees  really  escape  infection  therefore,  rather  than  actually  resisting 
it,  or  rather  they  escape  it  at  the  time  when  they  are  most  susceptible 
and  then  are  able  to  resist  any  later  infection  on  account  of  the  maturity 
of  their  tissues.  It  is  true,  however,  that  certain  individual  trees  have 
some  actual  resistance  to  the  disease,  even  at  susceptible  periods,  and 
those  having  such  immunity  are  of  course  the  most  desirable  type. 

In  seeking  blight-resistant  or  immune  walnut  trees  there  must  at  the 
same  time  be  kept  in  mind  the  fact  that  freedom  from  blight  is  not 
the  only  quality  necessary  in  the  walnut,  since  we  must  also  have  a 
tree  of  heavy  production,  with  nuts  of  desirable  size,  form,  color,  full- 
ness of  meat,  flavor  and  other  qualities  which  go  to  make  up  an  ideal 
walnut.  The  strongest  emphasis  should  also  be  laid  on  the  fact  that 
the  performance  of  a  single  tree  in  a  given  locality,  either  as  to  blight, 
bearing  qualities,  or  character  of  the  nuts  does  not  justify  its  exploita- 
tion for  all  parts  of  California  under  the  widely  different  conditions 
which  exist  in  different  localities.  Freedom  from  blight  in  a  certain 
tree  or  variety  in  a  given  locality  may  be  due  simply  to  the  fact  that 
the  disease  is  not  present  or  conditions  not  favorable  to  its  development 
in  that  particular  place.  "When  planted  in  another  locality  the  same 
variety  may  prove  to  be  one  of  the  very  worst  affected  by  blight.  Again, 
a  given  variety  may  produce  very  heavily  in  one  locality  under  certain 
climatic  conditions  and  not  in  another.  Again,  a  tree  may  be  free  from 
blight  and  produce  a  very  large  crop  of  nuts  one  year  or  even  for  several 
years,  and  then  later  on  develop  the  disease  very  badly  and  produce 
only  a  very  few  good  nuts.  Again,  a  tree  or  variety  may  be  actually 
immune  to  blight  to  a  large  extent  and  still  be  a  very  small  producer 
or  produce  nuts  of  an  undesirable  type  in  size,  form,  color,  flavor,  or 
some  other  characteristic.  Still  again,  a  variety  may  have  only  slight 
immunity  to  blight  and  yet  have  so  much  vigor  of  growth  and  tendency 
toward  heavy  production  that  the  resulting  crop,  in  spite  of  the  blight, 
will  be  much  larger  than  that  of  a  more  resistant  but  less  productive 
tree.     Still  further,  one  variety  may  produce  very  heavy  crops  of  nuts 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  369 

of  only  fair  quality,  while  another  may  be  a  small  producer  of  extra 
fancy  nuts.  All  these  and  other  considerations  go  to  show  that  one 
cannot  be  too  careful  and  conservative  in  recommending  and  exploit- 
ing a  variety  for  general  planting  on  the  basis  of  its  immunity  to  blight 
or  the  quality  and  quantity  of  its  product.  Only  after  several  years' 
experience  in  any  given  locality  can  the  qualities  of  a  certain  variety 
be  fairly  estimated,  and  even  then  its  behavior  in  other  localities,  where 
conditions  are  considerably  different,  cannot  be  safely  foretold  without 
actual  trial.  Many  a  walnut  grower  has  bought  high-priced  trees  from 
a  distance  on  account  of  enthusiastic  advertising  and  extravagant  praise, 
when  there  were  scores  of  trees  in  his  own  locality  which  might  have 
been  propagated  from  with  much  better  results  than  those  which  he 
will  obtain  from  his  high-priced  trees,  brought  from  a  distant  portion 
of  the  State,  where  the  whole  reputation  of  the  variety  rests  perhaps 
upon  the  performance  of  one  individual,  original  tree.  We  have  dis- 
cussed the  various  varieties  now  on  the  market  as  fully  as  possible  in 
another  place.  If  our  descriptions  and  estimations  seem  to  be  lacking 
in  positive,  definite  statements,  it  may  be  understood  that  this  is  not 
on  account  of  lack  of  acquaintance  with  the  varieties  mentioned,  but 
is  simply  due  to  the  fact  that  they  have  not  been  widely  tested,  and 
their  qualities  cannot  be  positively  stated  in  justice  either  to  the  variety 
or  to  the  public. 

The  control  of  walnut  blight  by  means  of  immune  varieties  presup- 
poses to  a  very  large  extent  the  planting  of  new  groves  in  place  of  the 
present  seedling,  irregular,  blight-susceptible  ones.  Many,  however, 
will  feel  that  such  a  solution  of  the  problem  falls  far  short  of  complete 
satisfaction  on  account  of  the  large  acreage  of  seedling  trees  now  in 
existence  which  have  cost  much  effort  and  expense  to  produce,  which 
would  be  fairly  profitable  were  it  not  for  the  blight,  and  which  it  is 
a  very  serious  matter,  or  perhaps  almost  entirely  out  of  the  question,  to 
think  of  replacing  with  new  trees  of  better  varieties.  Especially  in 
Orange,  Los  Angeles,  Ventura,  and  Santa  Barbara  counties  do  such 
groves  exist,  and  this  bulletin  would  not  be  complete  without  a  dis- 
cussion of  the  future  prospects  and  best  methods  of  handling  these 
seedling  groves,  composed  of  large  healthy  trees  in  normal,  thrifty 
condition,  save  for  the  attacks  of  blight  upon  the  crop. 

Working  Over  Seedling  Groves  to  Better  Varieties. — The  situation 
now  confronting  the  seedling  walnut  growers  of  California  is  not  a 
unique  one,  inasmuch  as  the  same  condition  has  confronted  in  turn 
the  growers  of  the  apple,  peach,  orange,  lemon,  and  all  our  other  culti- 
vated fruits.  The  seedling  orange  grove  is  still  with  us  to  a  consider- 
able extent,  and  the  seedling  apple  orchard  is  still  easily  within  the 
remembrance  of  the  present  generation.  It  is  not,  therefore,  an  unusual 
situation  which  the  walnut  grower  has  to  face,  and  he  may  rest  assured 

17—231 


370  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

that  it  will  eventually  result  in  the  entire  replacement  of  the  seedling 
tree  by  definite  varieties  propagated  by  grafting  or  budding.  In  our 
most  familiar  instance,  that  of  the  orange,  the  problem  of  what  to  do 
with  the  thrifty  old  seedling  grove  has  been  easily  solved  by  top-working 
these  trees  to  better  varieties.  With  the  orange  and  other  citrus  fruits 
this  is  a  comparatively  easy  operation.  With  the  walnut,  however,  it  is 
by  no  means  as  simple  and  yet  not  at  all  impossible.  A  few  growers, 
notably  one,  have  attacked  the  problem  in  this  way  with  very  excellent 
results.  Mr.  J.  B.  Neff,  of  Anaheim,  who  had  an  old  walnut  grove 
planted  as  seedling  trees,  commenced  a  systematic  effort  several  years 
ago  of  improving  his  trees  by  top-working.  For  several  years  he 
observed  the  grove  carefully,  picking  out  the  poorest-producing  and 
most  blight-susceptible  trees,  and  also  one  tree  which  seemed  by  far  the 
heaviest  producer  and  least  affected  by  blight  of  any  in  the  orchard. 
Having  located  his  very  poorest  trees  and  the  best  one,  he  commenced 
operations  by  cutting  off  the  tops  of  the  poor  trees  just  above  the  main 
forks  and  top-grafting  them  with  scions  from  the  good  tree.  The  suc- 
cess of  the  first  year's  grafting  was  very  good,  although  some  misses 
occurred  which  had  to  be  worked  over  again  the  next  year.  During  the 
second  year  more  trees  were  cut  off  and  worked,  and  with  the  working 
over  of  the  previous  year's  misses  the  whole  work  extended  over  three 
or  four  years  before  the  grove  reached  a  condition  satisfactory  to  the 
owner.  The  ultimate  outcome  has  been,  however,  that  the  average 
quality  and  productiveness  of  trees  were  very  much  increased,  and 
after  about  four  or  five  years  practically  all  the  grafted  trees  have  as 
large  tops  as  those  which  had  not  been  top-worked.  As  to  the  effect  of 
this  work  upon  the  production  of  the  grove,  Mr.  Neff  states  that  he  does 
not  think  that  the  cutting  off  of  the  poorest  trees  diminished  his  total 
crop  after  the  first  year.  One  eighth  of  all  the  trees  in  the  orchard 
were  top-grafted  the  first  year  and  one  fourth  of  the  total  trees  the 
second  year,  making  altogether  three  eighths  of  the  trees  which  were 
cut  off  and  worked  over.  The  total  number  of  trees  cut  off  and  grafted 
was  about  200.  In  1907,  the  year  previous  to  the  first  grafting,  the 
total  crop  was  20,406  pounds.  The  grafting  was  done  in  1908  and  1909. 
In  1911  the  total  crop  was  26,297  pounds.  During  the  intervening 
years  the  crop  was  smaller  than  in  either  1907  or  1911,  varying  consid- 
erably along  with  the  walnut  production  at  large  in  southern  California. 
Mr.  C.  B.  Franklin  of  Carpinteria  has  also  done  considerable  work 
along  this  line,  working  over  his  poorest  trees  into  better  kinds.  At 
the  Pasadena  City  Farm,  near  Alhambra,  a  large  number  of  seedling 
trees  about  six  years  of  age  have  been  worked  over  into  various  varie- 
ties, in  this  case  top-grafting  a  whole  row  or  a  solid  block  of  trees  at  one 
time  rather  than  picking  out  the  poorest  ones.  The  work  here  was 
quite  uniformly  successful  at  the  first  attempt  and  very  little  regrafting 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  371 

has  been  necessary.  Various  other  growers  have  top-worked  a  greater 
or  less  number  of  orchard  trees  with  varying  success.  The  whole 
matter  rests  largely  upon  the  skill  of  the  operator  who  does  the  grafting 
and  the  care  and  attention  given  to  the  trees  after  grafting  until  the 
new  tops  are  well  established.  Men  who  are  able  to  top-graft  the 
walnut  with  fairly  uniform  success  are  decidedly  uncommon  and  yet 
there  is  no  particular  mystery  or  secret  about  the  operation.  It  depends 
entirely  upon  mechanical  skill  in  this  sort  of  work,  knowledge  and 
judgment  of  the  peculiarities  of  the  walnut  tree,  and  particularly  upon 
great  care,  thoroughness  and  attention  to  details  in  selecting  and  keep- 
ing the  scions,  doing  the  grafting,  and  the  subsequent  care  of  the  grafts, 
especially  during  the  first  season.  Unless  prepared  to  give  the  work 
this  special  care  and  attention  until  new  tops  are  well  established  upon 
the  trees  we  would  not  advise  any  grower  to  attempt  to  improve  his 
walnut  grove  by  top-working.  If,  however,  he  can  give  the  work  such 
attention,  either  in  person  or  through  reliable,  competent  help,  we  would 
strongly  advise  any  grower  to  follow  Mr.  Neff's  example,  pick  out  his 
poorest  trees  and  work  them  over  into  a  better  variety,  either  by  select- 
ing scions  from  an  especially  good  tree  in  the  immediate  neighborhood 
or  by  putting  in  some  good  variety  among  those  which  we  describe 
elsewhere.  Again,  however,  we  would  emphasize  the  fact  that  if  the 
grower  cannot  undertake  this  work  with  the  assurance  of  giving  it 
careful,  continuous  attention,  he  would  much  better  leave  his  grove  in 
its  present  condition,  since  otherwise  he  will  find  himself  with  a  lot  of 
trees  composed  of  a  mass  of  sprouts  coming  from  the  cut-off  branches, 
the  latter  decaying  and  dying  back  in  the  stubs  where  they  were  cut, 
leaving  the  grove  in  much  worse  condition  than  before. 

Other  than  top-grafting,  the  only  method  of  bringing  about  improve- 
ment in  a  seedling  grove  is  by  means  of  more  regular  and  abundant 
irrigation,  pruning  and  thinning  out  the  tops  if  they  are  too  thick, 
heavy  fertilization  with  stable  manure  or  nitrogenous  fertilizers,  and 
such  other  improvements  in  cultural  practice  as  may  suggest  them- 
selves.    These  matters  we  have  discussed  on  pages  182-192. 

The  problem  of  the  seedling  walnut  grove  is  being  readily  solved  in 
many  portions  of  southern  California  by  the  rapidly  increasing  value 
of  land  and  the  prosperous  condition  of  the  citrus  industry.  Many 
hundreds  of  acres  of  thrifty  seedling  walnut  trees  have  been  cut  out  in 
Los  Angeles  and  Orange,  and,  to  some  extent,  in  Ventura  County,  during 
the  past  few  years,  and  planted  to  citrus  fruits,  especially  lemons.  At 
the  high  valuation  now  placed  upon  the  best  land  in  these  counties,  it  is 
doubtful  if  any  present  variety  of  walnut  could  compete  with  the  lemon 
or  Valencia  orange,  and  the  walnut  acreage  is  very  rapidly  being  trans- 
formed into  citrus  groves.  This  tendency  becomes  more  and  more  pro- 
nounced every  year. 


372  UNIVERSITY   OF    CALIFORNIA EXPERIMENT   STATION. 

DIE-BACK. 

The  most  conspicuous  disease  or  trouble  affecting  walnuts  in  southern 
California  is  that  characterized  by  this  name.    Two  general  types  of  die- 


Fig.   90. — Die-Back,  caused  by  dry  soil  and  cold  weather. 

back  may  be  distinguished,  one  on  old  trees,  particularly  hard  shells, 
which,  die  back  slowly  all  over  the  top,  and  another  occurring  suddenly 
during  a  single  winter  in  all  or  part  of  the  limbs,  which  may  die  back 


Bulletin    231]  WALNUT    CULTURE    IN    CALIFORNIA.  373 

down  to  the  main  forks  of  the  tree  or  the  tree  may  die  outright  clear  to 
the  ground.  The  former  type  of  die-back,  affecting  old  trees  slowly, 
occurs  mostly  on  light  soils  where  the  roots  find  insufficient  moisture  as 
they  become  crowded  together  and  extend  down  into  a  dry,  sandy  sub- 
soil. The  second  form  of  die-back  mentioned,  that  occurring  in  trees 
which  have  formerly  been  thrifty,  killing  them  down  to  the  forks  or 
even  to  the  ground,  is  sometimes  an  effect  of  frost,  but  occurs  especially 
with  or  without  freezing  in  cases  where  the  ground  has  become  too  dry 
during  the  fall  and  winter.  This  is  of  quite  common  occurrence  in 
walnut  groves,  especially  in  certain  seasons  when  the  rainfall  is  deficient 
during  the  fall  and  early  winter.  At  this  time  of  year  irrigation  of 
dormant  deciduous  trees  does  not  seem  to  be  urgent  and  serious  damage 
sometimes  occurs.  In  a  cold  locality  or  season  this  damage  may  be  very 
much  increased  by  frost,  when,  if  the  soil  had  been  sufficiently  moist,  no 
die-back  would  have  occurred.  The  remedy  is  therefore  obvious,  and  it 
is  significant  that  fall  and  winter  irrigation  of  walnut  groves  is  coming- 
much  more  into  practice  every  year.  It  may  be  said  in  general  that 
almost  all  die-back  of  walnut  trees  is  connected  with  the  matter  of  soil 
moisture.  Usually  it  is  the  direct  result  of  a  dry  subsoil,  although  in 
old,  closely  planted  groves  the  trouble  may  be  increased  by  a  lack  of 
proper  distance  between  the  trees,  deficiency  of  plant  food,  and  similar 
factors. 

Instances  are  sometimes  seen  when  the  opposite  condition  prevails, 
die-back  being  caused  by  an  excess  of  moisture  in  the  subsoil,  a  condi- 
tion of  which  the  walnut  tree  is  extremely  intolerant.  Such  damage 
may  be  seen  to  a  marked  extent  in  some  of  the  coastward  regions  of 
Ventura  County  and  in  other  parts  of  the  State,  where,  on  account 
of  floods  or  other  unusual  conditions,  the  ground  water  has  risen  in 
walnut  groves  close  to  the  surface. 


SUNBURN— BLACK  SAP. 

Serious  damage  is  sometimes  caused  from  this  source,  both  to  the 
fruit  and  the  tree.  This  w7e  have  already  discussed  to  some  extent  on 
page  177,  in  considering  the  relation  of  climatic  conditions  to  walnut 
culture.  The  sudden  occurrence  of  extremely  hot,  sunny  weather 
when  the  nuts  are  nearly  full  grown  may  produce  a  blackening  and 
burning  of  the  husk  on  one  side,  causing  the  husk  to  stick  to  the  shell, 
making  separation  difficult  and  causing  a  black  spot  which  may  extend 
through  into  the  meat.  Continuous  hot  weather  may  cause  a  darkening 
or  brownish  color  of  the  meat  which  would  otherwise  be  nearly  white, 
Avithout  a  burning  of  the  outer  husk.  This  varies  to  a  large  extent  in 
different  varieties. 


374  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 


Fig.   91. — Sunburn   or   "black-sap"    on   trunk. 


Bulletin   231] 


WALNUT    CULTURE   IN    CALIFORNIA. 


375 


On  the  tree  itself  the  trunk  is  frequently  affected  by  sunburn, 
causing  on  large  trunks  a  condition  frequently  called  by  the  growers 
"black  sap."  This  consists  of  a  considerable  area  on  the  south  or 
southwest  side  of  the  trunk  where  the  inner  bark  is  dead  and  from 
which  the  sap  of  the  tree  oozes  out,  oxidizing  and  turning  black,  as  is 
the  habit  of  walnut  sap  whenever  exposed  to  the  air.  This  form  of 
sunburn  occurs  more  commonly  in  the  winter  rather  than  in  the 
summer,  and  takes  place  at  times  when  the  days  are  hot  and  the 
nights  are  cold.  These  conditions  produce  an  irregular  activity  of 
the  sap,  which  causes  the  trunk  to  be  especially  susceptible  to  the 
heat  of  the  sun.  The  cambium  is  killed,  usually  on  the  southwest 
side  of  the  trunk,  and  the  sap  then  escapes,  oxidizes  and  ferments  in 
the  affected  area  and  a  large  wound  may  result  in  which  ordinary 


Fig.   92. — Sunburn  on  nuts. 

decay  sets  in.  It  is  on  account  of  this  form  of  sunburn  that  high 
grafting  on  black  walnut  stock  is  advocated  in  order  to  obtain  the  rough- 
barked  trunk  of  the  black  walnut.  We  have  seen  cases,  however,  when 
even  the  latter  was  affected  by  this  form  of  sunburn.  Young  trees 
during  their  first  year  after  planting  in  the  orchard  often  become 
badly  sunburned  in  the  trunk  and  on  this  account  should  be  protected 
after  planting,  as  discussed  on  page  253.  For  the  same  reason  it  is 
better  to  cut  the  trees  well  back  before  planting  and  grow  a  new  stem 
from  one  of  the  lower  buds,  as  described  on  page  251.  The  whole 
matter  of  sunburn,  either  on  the  fruit  or  the  wood,  is  influenced  to  a 
very  large  extent  by  the  moisture  conditions  of  the  soil.  In  all  cases 
trees  with  an  abundant  moisture  supply,  and  especially  if  in  fairly 
heavy  soil  of  good  water-retaining  properties,  are  much  less  affected 
by  any  form  of  sunburn,  either  summer  or  winter,  than  those  which 
are  suffering  for  water. 


376  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION. 

PERFORATION. 

This  has  come  to  be  one  of  the  most  serious  troubles  of  the  walnut 
grower  during  recent  years.  The  effect  is  that  shown  in  Fig.  93  and 
consists  in  a  non-development  of  the  outer  hard  layer  of  the  shell. 
The  meat  or  seed  of  the  walnut  is  covered  normally  by  four  different 
layers  of  tissue.  The  first  of  these  is  the  pellicle  or  seed  coat,  the  thin 
membrane  just  over  the  meat  which  adheres  closely  to  it  and  follows 


Fig.   93. — "Perforation"  of  walnuts. 

all  the  convolutions  and  irregularities  of  its  shape.  Outside  of  this 
is  what  we  call  the  shell,  which  consists  of  two  distinct  layers,  a  thin, 
inner,  parchment-like  one,  forming  the  lining  of  the  shell,  and  a  hard, 
bony  outer  layer.  The  fourth  coating  mentioned  is  composed  of  the 
husk  on  the  outside  of  the  nut  which  opens  and  allows  the  nut  to  fall 
out  at  maturity.  In  perforated  nuts  the  hard  shell  is  not  actually  per- 
forated, but  rather  fails  to  develop.  In  such  nuts  the  meat  and  pellicle 
develop  normally  and  over  them  the  thin,  inner  lining  of  the  shell. 


Bulletin   231]  WALNUT    CULTURE    IN    CALIFORNIA.  377 

The  hard,  outer  shell  is  deficient  and  fails  to  develop  properly.  This 
failure,  or  in  other  words  the  cause  of  perforation,  is  not  thoroughly 
understood,  but  is  probably  connected  with  one  of  two  factors,  or 
possibly  both.  These  are,  the  fertilization  or  pollination  of  the  nut  dur- 
ing the  blooming  period  and  its  nutrition  during  development.  Per- 
foration has  been  especially  abundant  under  two  conditions:  first,  in 
unusually  dry  years,  especially  when  the  trees  were  badly  affected  with 
the  walnut  aphis;  second,  in  young  trees  which  are  making  a  particu- 
larly thrifty  growth.  The  trouble  also  varies  to  a  considerable  extent 
in  individual  trees,  some  being  affected  every  year  and  others  never 
showing  this  trouble.  In  some  instances  there  has  been  some  indication 
that  the  trouble  was  worse  in  years  when  pollination  was  interfered 
with,  either  by  extremely  dry  weather  or  frost  during  the  blooming 
period.  This,  however,  is  not  well  established.  It  seems  most  probable 
that  the  disease  is  due  to  lack  of  nutrition  of  the  nuts  due  to  dryness  of 
the  soil,  exhaustion  of  the  trees  by  aphis  attacks,  or,  in  the  case  of  young 
trees,  a  vigorous  development  of  wood  at  the  expense  of  the  nuts.  If 
this  be  true  it  may  be  expected  in  the  case  of  young  trees  that  they 
will  gradually  outgrow  the  trouble  as  they  become  older  and  divert 
their  energies  more  toward  crop  production,  while  in  the  case  of  older 
trees  abundant  irrigation  throughout  the  year  and  the  control  of  aphis 
(which  we  discuss  elsewhere)  offers  most  promise  in  the  prevention  of 
perforation. 


CROWN  GALL. 

This  disease  which  is  common  in  most  fruit  trees  does  not  often 
affect  the  walnut  seriously,  although  now  and  then  a  badly  affected 
tree  like  that  shown  in  Fig.  94  may  be  found.  The  trouble  manifests 
itself  as  a  large  swelling  or  gall  at  the  base  of  the  trunk  either  just 
above  or  just  below  ground  or  both.  It  is  caused  by  a  bacterial  organism 
of  a  decidedly  parasitic,  infectious  nature. 

Occasionally  a  nursery  tree  is  found  affected  with  this  disease, 
although  it  is  very  much  less  common  in  the  walnut  than  in  the  peach, 
apricot,  almond,  apple  and  other  trees.  It  has  generally  been  sup- 
posed that  only  the  English  walnut  root  is  susceptible  to  crown  gall, 
but  we  have  recently  seen  a  case  of  a  northern  California  black  walnut 
root  badly  affected  with  this  trouble.  This,  however,  is  decidedly 
uncommon.  Any  nursery  tree  which  shows  this  trouble  should  be 
discarded.  Trees  affected  in  the  orchard  show  a  failure  of  growth, 
gradually  falling  behind  the  other  trees  in  size,  and  should  be  dug 
out  and  replaced  as  soon  as  detected.     The  galls  may  be  chiseled  out 


378 


UNIVERSITY   OF    CALIFORNIA EXPERIMENT   STATION. 


and  disinfected  with  some  success,  but  the  trouble  cannot  be  entirely 
overcome  in  this  way.  Usually  decay  sets  in,  as  shown  in  the  illustra- 
tion, and  the  tree  eventually  breaks  off.  • 


Fig.   94. — Crown  gall. 


ROOT  ROT. 

(OAK   FUNGUS— TOADSTOOL   DISEASE.) 

The  English  walnut  root  is  quite  susceptible  to  the  so-called  oak 
fungus  or  toadstool  disease,  which  occasions  the  loss  of  many  fruit 
trees  of  various  kinds  in  California.  This  disease  consists  in  a  decay 
of  the  roots,  in  which  the  white  mycelium  of  the  fungus  may  be  found 
between  the  affected  bark  and  wood.  Occasional  clusters  of  toadstools 
appear  at  the  base  of  affected  trees.  The  disease  usually,  if  not  always, 
occurs  in  spots  where  oak  trees  formerly  stood  and  when  once  started 
spreads  from  tree  to  tree  in  quite  a  regular  concentric  manner. 
Experience  has  amply  demonstrated  that  our  native  black  walnut  roots 
are  immune  to  this  fungus  and  we  have  seen  cases  where  English  walnut, 
prune,  almond  and  other  roots  have  been  picked  out  and  killed,  while 
northern  California  black  walnuts  interplanted  with  these  trees 
remained  entirely  unaffected.  It  is  altogether  probable  that  all  of  our 
black  walnut  species  and  hybrids  are  highly  resistant  if  not  totally 
immune  to  this  disease. 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  379 

SEEDLING  ROOT  ROT— WILT. 

Nursery  seedlings  of  the  southern  California  black  walnut  occa- 
sionally wilt  and  die  rather  suddenly  and  show,  on  examination,  a 
black  rot  of  the  main  root  just  below  ground.  This  may  appear  either 
before  or  after  grafting,  and  ordinarily,  at  the  worst,  picks  out  only 
a  tree  or  two  here  and  there,  even  in  a  large  nursery.  We  have  known 
of  only  one  case  where  serious  loss  was  experienced  from  this  source, 
and  this  on  poorly  drained  land  where  the  trees  were  injured  by  an 
excess  of  water.  The  trouble  is  caused  by  a  soil  fungus,  and  seems  to 
be  confined  to  the  southern  California  black. 


LITTLE  LEAF,  "YELLOWS." 

In  this  disease  spindling  yellow  shoots  develop  wihch  usually  die 
back  from  the  top.  All  degrees  of  the  trouble  may  'occur  from  slightly 
unnatural  yellowing  and  slenderness  of  the  normal  shoots  to  the  produc- 
tion of  abnormal  clusters  of  small,  yellow,  sickly  shoots  with  very  slen- 
der, yellow,  poorly  developed  leaflets.  Such  shoots  in  bad  cases  usually 
die  back  at  the  end  of  each  season.  This  disease  affects  the  English 
walnut  and  is  even  more  pronounced  on  the  northern  California  black 
in  certain  seasons  and  places.  It  has  been  abundant  even  on  black 
walnut  trees  of  large  size  in  some  parts  of  northern  California  during 
the  last  two  or  three  years  and  very  prevalent  in  nursery  trees  of  the 
northern  California  species  grown  in  the  southern  part  of  the  State. 
The  southern  California  black  walnut  is,  so  far  as  our  experience  goes, 
immune  to  this  disease,  while  the  Paradox  and  Royal  hybrids,  especially 
the  latter,  are  much  less  susceptible  to  it  than  either  the  English  or 
northern  California  black.  This  disease  is  not  confined  to  the  walnut 
but  is  evidently  the  same  as  the  so-called  "Little  Leaf"  of  the  grape, 
peach,  apple,  quince  and  umbrella  tree2  and  the  mottled  leaf  of  the 
orange.  The  "Frizzles"  or  "Rosette"  of  the  pecan  seems  also  to  be 
of  a  similar  nature.  Experience  has  shown  beyond  any  reasonable 
doubt  that  the  occurrence  of  all  these  troubles  has  been  the  result  of 
the  abnormally  long  dry  seasons  of  the  past  three  years.  These  diseases 
have  occurred  particularly,  or  in  fact  altogether,  on  soils  where  for  any 
reason  the  subsoil  has  become  very  dry  during  the  latter  part  of  the 
season.  Such  condition  has  been  most  commonly  caused  by  sandy  or 
gravelly  subsoil  but  may  also  result  from  the  presence  of  hardpan  or 
a  layer  of  heavy  soil  within  two  or  three  feet  of  the  surface.  The  con- 
trol of  this  trouble  lies  entirely  in  irrigation,  especially  in  the  late 
summer  and  fall  during  seasons  when  the  rains  are  late  in  commencing. 


380 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


If  the  soil  is  kept  well  watered  during  this  period  this  disease  need 
not  be  feared.  In  the  case  of  hardpan  or  heavy  soil  underlaid  by 
dry  subsoil  some  growers  have  resorted  to  the  practice  of  blasting  with 


Fig.   95. — Little    leaf    or    yellows ;    on    northern    California    black    above,     on 
English   at  the   left  below.      Normal   branch   at   the   right. 

dynamite  in  order  to  let  the  water  down  through  into  the  subsoil.  We 
believe  this  to  be  an  excellent  method  of  procedure.  The  most  impor- 
tant factor  in  the  prevention  or  avoidance  of  little  leaf  lies  in  the  choice 


Bl'LLETIX     23  1   I 


WALNUT    CULTURE    IN    CALIFORNIA. 


381 


of  a  root  for  the  walnut.  Also  the  selection  of  soil  upon  which  to 
plant  this  crop.  Land  having  a  sandy  or  gravelly  subsoil  within  four 
or  five  feet  of  the  surface  should,  if  possible,  be  strictly  avoided  for 
planting  a  walnut  orchard.  The  same  is  true  of  soil  underlaid  by 
hardpan.     In    any   case   it   is   very   desirable   to  blast  each   hole   with 


Fig.  96. — Placentia  walnut  tree  on  English  root,  affected  by  yellows.  Trees  like 
that  shown  in  Fig.  63,  on  southern  California  black  root,  are  of  same  age 
and   interplanted   alternately   with    these. 

dynamite  before  planting  in  order  that  the  subsoil  may  be  shaken  up 
and  easy  access  of  water  permitted.  No  tree  already  affected  with 
this  disease  should  be  grafted,  either  in  the  nursery  or  in  the  case  of 
black  walnut  trees  planted  in  orchard  form.  The  pervalence  of  this 
trouble  is  another  argument  in  favor  of  the  hybrid  root  or  the  southern 


382  UNIVERSITY   OF    CALIFORNIA EXPERIMENT   STATION. 

California  black,  the  latter  at  least  in  the  southern  part  of  the  State, 
or  for  varieties  which  come  out  early  in  the  spring.  A  very  good  illus- 
tration of  the  difference  in  respect  to  this  disease  produced  by  differ- 
ent roots  was  seen  in  a  walnut  orchard  near  Whittier  during  the  past 
season.  In  this  case  trees  of  the  Placentia  Perfection  variety  had  been 
double  planted,  the  permanent  trees  on  southern  black  root  and  the 
fillers  on  English.  During  the  latter  part  of  the  season  of  1911  the 
difference  between  the  trees  on  the  two  roots  was  very  marked,  those  on 
the  English  being  smaller,  with  yellow  foliage  and  narrow  leaflets,  the 
leaves  falling  to  the  ground  early  in  the  fall.  The  alternate  trees  on 
southern  California  black  root  were  larger,  bore  a  better  crop  and  had 
dark  green,  vigorous  looking  foliage  which  remained  on  the  trees  much 
later  than  that  of  the  other  trees. 


SHRIVELED  MEAT. 

Much  trouble  is  experienced  with  walnuts  in  certain  seasons  on 
account  of  the  meat  being  shriveled  and  poorly  developed.  This  affects 
some  varieties  and  some  individual  trees  more  than  others  and  is  often 
much  worse  the  same  year  in  certain  localities  than  in  others.  The 
trouble  is  more  apt  to  affect  varieties  which  come  out  late  in  the  spring 
than  those  which  develop  early.  It  is  usually,  though  not  always, 
worse  on  such  varieties  in  the  southern  part  of  the  State  than  in  the 
northern,  and  this  indeed  is  one  of  the  principal  reasons  why  very  late 
varieties  are  not  adapted  to  southern  California.  A  tendency  toward 
this  trouble  is  one  of  the  worst  faults  of  the  Eureka  in  the  southern 
part  of  the  State,  and  the  same  is  true  of  Franquette,  Hale,  Concord, 
San  Jose,  and  in  fact  almost  every  late  variety  that  has  been  tested  in 
southern  California.  The  northern  part  of  the  State  is  by  no  means 
free  from  this  trouble,  but  it  is  less  common  there  and  is  usually  con- 
fined in  certain  seasons  to  certain  localities,  although  it  does  not  affect 
the  same  locality  every  year.  In  1911,  for  instance,  the  Franquettes 
were  quite  generally  poorly  filled  and  light  meated  in  Sonoma 
County,  while  in  the  vicinity  of  San  Jose  and  Stockton  such  was  not 
the  case.  In  other  or,  in  fact,  in  most  years,  Sonoma  County  Fran- 
quettes have  been  as  well  filled  as  any.  The  cause  of  this  poor  devel- 
opment or  shriveling  of  the  meat  has  been  ascribed  to  various  influences, 
none  of  which  have  been  positively  proven  to  bring  about  this  trouble. 
The  influences  suspected  have  been  the  same  as  those  to  which  per- 
foration or  non-development  of  the  shell  have  been  laid,  namely  poor 
pollination,  lack  of  soil  moisture,  and  the  attacks  of  the  walnut  aphis. 
Which  of  these  actually  causes  the  trouble  has  not  been  positively 
determined.     In  the  southern  part  of  the  State  it  is  probable  that  the 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  383 

pollination  of  late  varieties  is  hindered  by  extremely  dry  weather  which 
is  likely  to  occur  at  the  time  when  they  are  in  bloom,  and  it  is  also 
true  that  during  the  season  of  1911  late  spring  frosts  occurred  in 
many  localities  in  the  northern  part  of  the  State,  which  may  have 
interfered  with  the  proper  setting  of  the  crop.  Aphis  has  likewise 
been  very  abundant  during  the  last  two  or  three  years,  and  this  con- 
dition has  been  coincident  with  short  rainfall  and  lack  of  soil  moisture, 
especially  in  the  subsoil.  While  the  disease  cannot  at  present  be 
attacked  specifically,  we  believe  that  its  control,  along  with  that  of 
perforation,  yellow  leaf,  and,  in  fact,  most  of  the  troubles  which  affect 
the  walnut  will  be  greatly  contributed  to  by  the  control  of  the  aphis 
and  attention  to  proper  irrigation  of  the  subsoil.  The  latter  can  usually 
be  readily  accomplished  where  irrigation  water  is  available  and  the 
grower  should  watch  carefully  the  moisture  condition  of  his  subsoil  in 
dry  years  by  actual  examination  down  to  a  depth  of  at  least  six  feet. 
Where  no  irrigation  is  possible  dry  farming  methods  should  be  sys- 
tematically pursued,  consisting  in  deep  plowing  so  as  to  catch  as  much 
as  possible  of  the  winter  rainfall  and  deep  and  thorough  summer 
cultivation  to  retain  such  moisture  in  the  ground.  The  control  of 
aphis  we  discuss  under  the  next  heading. 


APHIS. 

The  walnut  is  comparatively  free  from  insect  enemies,  and  we  shall 
not  attempt  to  present  a  complete  description  of  every  insect  which 
may  at  times  be  found  attacking  the  tree.  One  enemy  of  this  sort, 
however,  is  of  particular  importance  and  should  be  mentioned  here. 
This  is  the  green  aphis  or  plant  louse.  This  insect  has  become  so 
abundant  during  the  past  two  years  on  walnut  trees  of  almost  every 
species  all  over  the  State  that  it  may  be  considered  fully  as  important 
as  the  much  dreaded  walnut  blight. 

The  walnut  aphis  is  a  small,  soft,  green  insect  which  occurs  on  the 
under  side  of  the  leaves,  often  in  considerable  abundance.  The  insect 
itself  is  less  conspicuous  than  the  secondary  effects  which  it  produces. 
These  are,  first,  an  abundant  secretion  of  honeydew,  a  sticky,  liquid 
substance  with  which  the  foliage  and  the  ground  or  vegetation  beneath 
the  trees  becomes  covered.  The  second  conspicuous  effect  consists  in 
the  development  of  a  black,  smutty  mold  which  grows  upon  this 
honeydew  and  covers  the  leaves  and  fruit  of  the  walnut  and  every- 
thing else  upon  which  the  honeydew  has  dropped.  This  insect  and 
its  attendant  effects  have  always  been  common  in  occasional  seasons, 
but  during  the  past  two  years  there  has  been  an  unusual  prevalence 
of  aphis  in  most  parts  of  the  State,  both  on  English  and  black  walnut 


384  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

trees.  The  insect  feeds  by  sucking  the  nutritive  juices  from  the 
foliage  of  the  tree  and  when  abundant  it  may  injure  the  tree  to  no 
little  extent  by  so  doing.  In  dry  years,  when  the  trees  are  already 
somewhat  weakened,  the  bad  effects  are  increased.  It  is  also  probable 
that  the  tree  is  injured  more  or  less  by  being  coated  over  with  honeydew 
and  sooty  mold.  The  insect  multiplies  most  freely  in  seasons  or  places 
of  rather  cool,  moist,  summer  climate,  and  is  largely  suppressed  by 
continuous  hot  sunshine.  Its  effects  are  therefore  worst  in  regions 
near  the  coast.  In  addition  to  the  direct  injury  to  the  tree  caused  by 
the  aphis  and  its  honeydew,  there  is  some  possibility  that  these  effects 
are  connected  with  perforation  of  the  walnut  and  also  shriveling  or 
poor  development  of  the  meat.  In  all  events  these  troubles  usually 
occur  together,  and  years  when  there  is  an  abundant  development  of 
aphis,  there  has  also  usually  been  more  perforation  and  more  poor 
meats.  This  may  be  the  effect  of  the  insect  or  it  may  be  that  all  these 
troubles  occur  more  abundantly  under  the  same  conditions,  partic- 
ularly in  a  season  following  a  dry  winter.  Another  well-established 
effect  of  the  aphis  is  connected  with  the  spread  of  the  walnut  blight 
organism.  There  is  no  question  that  these  insects  in  crawling  about 
and  puncturing  the  leaves  spread  the  blight  to  a  considerable  extent. 
All  in  all,  therefore,  we  believe  that  the  control  of  aphis  is  one  of  the 
most  important  problems  of  the  walnut  grower  if  the  insect  continues 
to  develop  as  it  has  during  the  past  two  or  three  years. 

APHIS   CONTROL. 

The  only  feasible  means  of  controlling  this  insect  appears  to  be  by 
spraying  with  the  most  effective  substance  at  the  most  effective  time. 
No  definite  experiments  have  been  made  along  this  line,  nor  has  the 
insect  ever  been  carefully  studied  so  far  as  we  are  aware.1  It  appar- 
ently winters  over  upon  the  walnut  tree,  probably  in  the  egg  form, 
so  that  it  may  be  possible  by  a  winter  spraying  to  exterminate  the 
insect  during  the  dormant  season.  Various  winter  spraying  of  wal- 
nuts has  been  done  by  different  growers,  using  lime-sulphur  and  other 
similar  sprays.  The  results  of  such  spraying  as  to  aphis  control  seem 
to  be  somewhat  doubtful.  Some  have  thought  that  much  benefit  was 
obtained,  the  amount  of  aphis  during  the  following  summer  being  much 
reduced,  while  others  could  see  no  such  effect.  Summer  spraying  is 
effective  against  many  other  kinds  of  plant  lice,  and  there  is  no  reason 
why  the  walnut  aphis  could  not  be  controlled  in  the  same  way,  except 
that   the   trees   are   large   and   the   spraying   expensive.     Mr.    George 


nt  is  described  and  illustrated  by  E.  O.  Essig-  in  The  Monthly  Bulletin,  Cal.   State 
Com.  of  Hort.,  Vol.  1,  No.  5,  p.  190. 


Bulletin    231]  WALNUT    CULTURE   IN    CALIFORNIA.  385 

Williams  of  Goleta  has  done  a  considerable  amount  of  summer  spraying 
with  a  tobacco  spray  with  very  satisfactory  results.  The  following 
mixtures  may  be  suggested  for  work  of  this  sort.1  In  applying  them  a 
special  effort  should  be  made  to  spray  the  under  side  of  the  leaves,  as 
this  is  where  the  insects  are  found.  Spraying  should  be  done  as  early 
in  the  season  as  possible  in  order  to  exterminate  the  insects  before  they 
multiply.  It  is  hoped  that  systematic  experiments  along  this  line  may 
be  made  during  the  coming  season. 

Soap   Solution. 

Soap    1    pound. 

Water   5    to   15    gallons. 

Whale-oil  or  fish-oil  soap  preferable,  but  for  small  amounts  any  yel- 
low laundry  soap  will  answer. 

Tobacco  Soap. 

Blackleaf  40 1  pound  (1-10  gallon). 

Cresol  soap,  1  gallon  or  whale-oil  soap 10  pounds. 

Water    200     gallons. 

The  cresol  soap  requires  no  heating. 


BLISTER  MITE— ERINOSE. 

This  is  a  very  common  trouble  of  the  walnut  tree  but  not  a  serious 
one.  Its  effects  are  seen  in  the  form  of  blister-like  swellings  or  eleva- 
tions on  the  leaf  surface,  wThich  are  convex  on  the  upper  and  concave 
on  the  lower  side  of  the  leaf.  These  swellings  are  caused  by  numerous, 
very  small  insects  which  live  within  the  blisters  on  the  under  side  of 
the  leaf  amongst  a  felt-like,  hairy  growth  which  develops  there.  While 
this  effect  is  very  common,  it  produces  no  appreciable  injury  and  needs 
no  treatment  for  its  control. 


RED  SPIDER. 

This  is  a  very  small  mite  which  sometimes  becomes  extremely  abun- 
dant on  walnut  leaves,  causing  them  to  dry  and  even  to  fall  from  the 
tree.  The  insect  is  not  ordinarily  serious  except  in  very  hot  climates,  to 
which  the  walnut  is  not  well  adapted.  In  such  situations  red  spider 
usually  hastens  the  dropping  of  the  leaves  caused  by  too  intense  sum- 
mer heat. 


'Circular  66,  Cal.  Agr.  Expt.  Sta. 

18—231 


386  UNIVERSITY   OF    CALIFORNIA EXPERIMENT   STATION. 

APPENDIX. 


WALNUTS  IN  FRANCE. 

We  have  thought  it  worth  while  to  present  excerpts  from  a  trans- 
lation of  the  following  excellent  article  by  Mr.  F.  Lousourd,  taken 
from  Revue  Horticole,  volume  83,  1911,  pages  310,  329,  358,  378. 

' '  We  prefer  to  study  the  varieties  by  regions  and  have  divided  them 
into  three  groups. 

1.  Nuts  of  the  Southeast. 

2.  Nuts  of  Central  France. 

3.  Varieties  Belonging  to  Various  Regions. 

This  classification  has  some  advantages;  the  varieties  cultivated  in 
the  same  region  prove  to  be  similar,  and  the  comparison  of  character- 
istics is  thus  easy. 

NUTS  OF  THE  SOUTHEAST. 

Mayette. — The  Mayette  walnut  is  large,  slightly  elongated,  widened 
and  flattened  at  the  base,  even  slightly  depressed  toward  the  peduncle. 
It  easily  stands  upright  on  its  base,  and  this  characteristic  alone 
suffices  to  distinguish  it  from  other  varieties  of  the  Isere  to  which  it 
has  some  resemblance.  The  shell,  half-hard,  of  a  light  amber  color, 
terminates  at  the  apex  in  an  obtuse,  somewhat  pronounced  point;  it 
protrudes  slightly  along  the  suture  of  the  valves  from  the  lower  third 
as  far  as  the  point.  The  average  dimensions  of  the  walnut  are  as 
follows:  length  44  mm.,  breadth  34  mm.;  it  weighs,  dry,  from  10  to 
11  grammes.  A  hectolitre  (2.85  bushels)  of  the  dry  walnuts  weighs 
from  30  to  33  kilogrammes  (66  to  73  pounds). 

The  origin  of  this  variety  is  very  obscure.  It  gets  its  name  from  the 
name  Mayet  who,  according  to  some,  imported  it  from  Naples  and 
according  to  others  obtained  it  from  seed.  It  has  been  cultivated  nearly 
one  hundred  and  fifty  years  in  the  department  of  Isere,  where  it  is 
located  within  the  cantons  of  Tullins,  Vinay  and  Saint-Marcellin.  It 
is  found  on  the  well  exposed  terraces  bordering  both  banks  of  the  Isere 
from  Moirans  to  Vinay. 

Of  all  the  varieties  of  walnuts  cultivated  in  France,  the  Mayette  is 
the  most  beautiful.  The  fine,  fair  shell,  well  filled,  contains  a  kernel 
possessing  the  delicate  flavor  of  the  hazelnut.  The  nut  for  dessert  is 
par  excellence,  and  when  the  crop  is  light  the  merchants  dispute  over 
the  price.  It  always  sells  for  a  greater  price  than  other  varieties; 
in  an  ordinary  year  it  brings  from  75  to  80  francs  per  100  kilogrammes, 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  387 

dry.  (About  7  cents  per  pound.)  The  highest  price  for  which  this 
is  sold  ranges  from  110  to  120  francs  (10  to  11  cents  per  pound).  It 
is  always  sold  in  the  shell ;  it  is  exported  to  foreign  countries,  especially 
to  the  United  States. 

The  Mayette  is  a  walnut  of  Isere  which  dries  better,  and,  at  the 
same  time,  whose  yield  is  most  assured  in  a  soil  and  climate  which 
favors  its  culture.  But  this  variety  is  very  exacting  and  in  the  valley 
of  Gresivaudan  it  scarcely  exceeds  an  altitude  of  400  meters  (1300 
feet  above  sea  level)  ;  if  it  is  cultivated  beyond  this  limit,  it  loses  in 
quality.  On  the  other  hand  it  requires  fertile  soil  and  abundant  and 
regular  manuring. 

In  spite  of  its  quality,  which  places  it  in  the  first  rank  of  table  nuts, 
it  is  hardly  probable  that  the  Mayette  will  extend  outside  the  area 
which  it  occupies  in  the  department  of  Isere.  Moreover,  the  agricul- 
turists in  regions  producing  the  Mayette  are  making  an  effort  to  limit 
it.  For  some  years  there  have  been  planted  here  and  there  (Haute- 
Savoie,  Cher,  etc.)  some  walnut  trees  of  this  variety;  it  is  still  too  early 
to  form  any  conclusions  from  present  results. 

The  tree  is  vigorous  and  blossoms  late  but  rapidly.  In  consequence 
it  makes  a  fine  sight.  It  is  fitting  to  add  that  in  the  above  mentioned 
cantons,  the  Mayette  comprises  nine  tenths  of  the  orchards.  It  con- 
stitutes orchards  whose  mass  of  stately  trees  give  a  picturesque  aspect 
to  the  country.  In  a  certain  number  of  townships  of  Isere,  the  pro- 
ducts of  the  Mayette  tree  form  the  principal  resources  of  the  agricul- 
turist. 

Parisienne. — The  Parisienne  nut  is  large,  oblong  and  nearly  as  wide 
at  the  top  as  at  the  base.  It  stands  less  easily  on  the  base  than  the 
Mayette.  The  point,  the  apex  of  the  shell,  is  almost  imperceptible. 
This  is  somewhat  hard,  rather  rough  and  of  dark  color. 

The  average  dimensions  are  as  follows :  length  40  mm.,  width  36  mm. 
The  average  weight  of  a  hectolitre  (2.85  bushels)  of  dry  nuts  varies 
from  30  to  33  kilogrammes  (66  to  73  pounds). 

Like  the  Mayette,  the  Parisienne  is  a  special  variety  of  the  depart- 
ment of  Isere.  The  crop  is  produced  especially  in  the  canton  of  Vinay 
and  somewhat  in  the  canton  of  Saint-Marcellin.  The  color  is  less 
fine  than  that  of  the  Mayette,  but  the  kernel  is  good  and  completely 
fills  the  shell.  Although  less  choice  than  the  Mayette,  and  selling  for 
less,  it  is,  nevertheless,  one  of  the  better  varieties  for  dessert.  It  is 
less  exacting  than  the  Mayette  and  may  thrive  at  an  altitude  exceeding 
400  meters. 

The  tree  is  vigorous,  flowering  late  and  for  rather  long  duration, 
which  favors  its  resistance  to  spring  frosts  and  assures  regularity  of 
crops.     The  crops  are  quite  large. 


388  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

Franquette. — This  variety  was  found  by  Franquet,  a  litte  less  than 
a  hundred  years  ago,  close  by  the  Notre  Dame  d 'Osier  (a  town  in 
the  vicinity  of  Saint-Marcellin).  The  Franquette  nut  is  large,  elon- 
gated, narrow,  exceedingly  pointed,  the  apex  terminating  in  a  very 
pronounced  point.  The  shell,  hard  and  of  a  dark  color  (?),  presents 
a  pronounced  depression  along  each  rib  of  the  line  of  suture  of  the 
valves;  it  is  rough  and  very  wrinkled.  The  green  kernel  fills  the 
cavity  well  and  the  dry  kernel  is  of  good  quality  though  inferior  to 
that  of  the  Mayette.  The  average  dimensions  are  as  follows:  length 
48  mm.,  width  37.  The  average  weight  of  a  hectolitre  (2.85  bushels) 
of  dry  nuts  varies  between  33  and  35  kilogrammes  (73  to  77  pounds). 

The  Franquette  walnut  is  located  in  the  department  of  Isere,  where 
it  abounds  on  the  hills  situated  between  Vinay  and  Saint-Marcellin. 
The  tree  is  vigorous,  spreading,  flowering  late;  it  produces  regularly 
and  thrives  well  in  dry  soil.  The  fruits  are  exported  in  shell  to 
America.  They  bring  on  an  average  5  francs  less  per  quintal  than 
those  of  the  Mayette. 

The  three  varieties  described  above  (Mayette,  Parisienne,  Fran- 
quette) are  designated  in  commerce  by  the  name  Noix  de  Grenoble 
(Grenoble  nut). 

Noix  de  Vourey. — The  Vourey  walnut  is  scarcely  harvested  except 
in  the  town  of  Vourey  (Isere)  and  in  neighboring  localities.  It  has 
somewhat  the  shape  of  the  Mayette,  although  it  is  smaller.  It  is  a 
nut  of  average  size,  a  little  elongated,  slightly  flattened  at  the  base, 
and  terminating  at  the  apex  in  a  very  pronounced  point.  The  shell 
projects  along  the  line  of  suture  of  the  valves,  extending  from  the 
lower  third  to  the  point.  The  average  dimensions  are  as  follows : 
length  35  mm.,  width  29  mm. 

This  is  a  nut  of  two  purposes,  good  for  table  use  and  very  good 
for  the  manufacture  of  oil.  Its  shell,  very  thin  and  tender,  of  a  clear 
color,  presents  a  good  appearance;  the  kernel  is  of  good  quality. 
The  Vourey  nut  is  not  held  in  reproach  for  its  small  size ;  but  in  spite 
of  its  size,  it  is  sold  partly  in  shell  for  dessert,  and  very  often  it  is 
cracked  and  sold  as  green  kernels  which  are  fine  and  fill  the  shell 
well.  From  the  last  point  of  view  it  is  a  very  choice  variety.  Besides, 
it  bears  from  the  third  year.  It  is  more  precocious  than  the  Mayette, 
the  Parisienne  and  the  Franquette. 

The  tree  is  vigorous,  spreading  and  very  productive.  It  blossoms 
late  (on  an  average  ten  to  twelve  days  after  the  Mayette  and  Fran- 
quette). 

Meylan. — This  is  originally  from  Meylan  (Isere),  where  its  culture 
is  nearly  nil,  nearly  all  the  trees  of  the  Persian  type  being  on  the  road 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  389 

to  disappearance.  But  it  is  found  here  and  there  in  the  department 
of  Isere. 

This  nut  is  large  or  very  large,  round,  flattened  at  the  base,  slightly 
pointed  at  the  apex.  The  shell,  of  a  clear  color,  is  soft  and  nearly 
smooth.  The  large,  delicate  kernel  fills  the  cavity  well.  The  dimen- 
sions are  as  follows :  length  38  mm.,  width  36  mm. 

The  Meylan  blossoms  late  and,  for  this  reason,  it  escapes  nearly  all 
the  spring  frosts ;  its  crop  is  a  little  more  sure,  especially  in  a  year  not 
wholly  favorable  for  the  production  of  the  walnut.  The  tree  is  vig- 
orous and  very  spreading.  For  purchase  when  mature,  this  variety 
is  not  as  popular  as  the  Mayette,  which  is  ideal  for  dessert.  It  sells 
for  a  little  less,  but  the  tree  being  less  delicate  and  less  exacting  as 
regards  climate  and  fertility  of  the  soil,  the  Meylan  will  give  very 
good  results  in  a  place  not  suited  to  the  Mayette. 

Gautheronne. — The  Gautheronne  is  little  known.  However,  the  trees, 
are  scattered  here  and  there  in  the  canton  of  Tullins,  (Isere).  It  has 
very  much  the  shape  of  the  Chaberte,  but  it  is  larger  and  its  shell  is 
smoother  and  the  color  clearer.  It  measures  40  mm.  in  length  and 
32  mm.  in  width.     It  is  sold  in  the  shell  for  dessert. 

Chaberte. — This  gets  its  name  from  Chaberte,  its  originator  and  pro- 
pagator; it  has  been  cultivated  for  a  hundred  and  fifty  years  around 
the  environs  of  the  department  of  Isere.  It  is  a  nut  small  or  of  aver- 
age size,  a  little  elongated,  slightly  pointed,  having  a  hard,  wrinkled 
shell  of  dark  color  and  very  full;  its  kernel  is  delicate.  The  average 
dimensions  of  the  nut  are,  length  35  mm.,  width  30  mm.  The  nut, 
dry,  weighs  about  9  grammes  and  the  weight  of  a  hectolitre  (2.85 
bushels)  varies  from  36  to  40  kilos  (79  to  88  pounds). 

The  Chaberte  blossoms  late,  almost  as  late  as  the  Saint-Jean,  which 
it  replaces  advantageously.  The  tree,  vigorous  and  productive,  yields 
regular  crops.  It  is  cultivated  in  Isere,  within  the  plateau  of  Bizoir 
from  Voiron  to  Lyons.  It  is  found  in  all  the  districts  except  those  of 
Saint-Marcellin.  It  is  also  cultivated  in  Savois,  in  the  Drome  and  in 
a  few  departments  in  central  France. 

It  is  utilized  for  the  manufacture  of  oil;  and  especially  since  the 
fresh  kernels  demand  a  high  price,  they  crack  the  nuts  and  pack  the 
kernels  in  cases  which  are  exported  to  America.  According  to  M. 
Rouault,  Departmental  Professor  of  Agriculture  of  Isere,  the  yield  of 
oil  is  64  per  cent  or  12  litres  (10.8  quarts)  of  oil  to  20  kilograms  (44 
pounds)  of  kernels,  but  in  practice  they  count  on  one  litre  of  oil  to 
2  kilograms  of  kernels.  The  Chaberte  (oil)  pays  at  most  from  26  to 
32  francs  ($5.20  to  $6.40)  a  hectolitre  (26J  gallons),  a  price  which  is 
rarely  exceeded;  in  ordinary  years  it  varies  from  15  to  28  francs  per 
100  kilos  ($3  to  $5.60  per  220  pounds). 


390  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

Petite  Ronde. — The  Petite  Ronde,  peculiar  to  the  department  of 
Drome,  where  it  is  principally  cultivated  in  the  districts  of  Die,  is,  as 
its  name  indicates,  a  nut  of  small  dimensions.  It  measures  on  an 
average  31  to  32  mm.  in  length  by  30  mm.  in  width  and  weighs,  dry, 
from  6  to  7  grammes.  A  hectolitre  (2.85  bushels)  weighs  40  kilos 
(88  pounds). 

It  is  almost  as  wide  as  it  is  high,  large  at  the  top  and  slightly 
depressed  from  the  shoulder  to  the  point,  which  is  small,  but  pro- 
jecting. The  shell  is  rounded  in  the  region  of  the  base,  which  makes 
it  rather  unstable  on  its  base.  The  shell  projects  a  little  along  the 
line  of  suture  of  the  valves  in  the  upper  half. 

The  Petite  Ronde  is  of  a  beautiful  dark  yellow  color;  it  is  culti- 
vated for  sale  fresh  (for  confectionery)  and  for  sale  of  the  fresh 
kernels.  There  are  3  kilograms  (6.6  pounds),  500  green  kernels,  in  a 
double  decalitre  (2 J  pecks)  of  walnuts.  The  tree  blossoms  late.  It 
yields  large  crops. 

NUTS  OF  CENTRAL  FRANCE. 

Car  erne. — The  Careme  is  a  little  elongated,  having  a  medium  point 
and  a  shell  flattened  and  also  slightly  and  irregularly  depressed  at  the 
base.  The  shell  is  projectile  along  the  suture  of  the  valves  extending 
from  the  middle.  It  is  thin,  tender,  with  a  dull,  very  wrinkled  sur- 
face. It  is  of  average  size,  36  mm.  in  length  by  32  mm.  in  width. 
The  average  weight  of  a  dry  nut  is  8J  grammes  and  the  weight  of  a 
hectolitre  (2.85  bushels)  varies  from  34  to  36  kilos  (75  to  80  pounds). 

The  Careme  is  principally  cultivated  in  the  department  of  Aveyron, 
particularly  in  the  district  of  Villef ranche-de-Rouergue ;  the  greater 
part  of  the  walnut  trees  of  the  department  are  of  this  variety,  which 
has  for  its  origin  an  old  and  magnificent  tree  situated  on  the  route  from 
Capdenac,  one  kilometer  to  the  north  of  Villeneuve.  This  old  tree 
has  a  trunk  measuring  only  2  to  2J  meters  in  height,  and  strong  limbs 
which  extend  laterally  through  a  radius  of  from  10  to  12  meters;  it 
has  formerly  yielded  as  much  as  6  hectolitres  (17  bushels)  of  nuts.  It 
is  this  which  has  furnished  grafts  for  nearly  all  the  trees  in  the  country. 
The  tree  is  spreading  and  bears  well. 

The  Careme  is  sometimes  sold  for  the  table.  It  is  very  much  valued 
for  the  sale  of  the  green  kernels.  Its  shell  is  thin  and  the  kernel  fills 
it  well,  with  no  waste  space,  the  kind  of  nut  which  has  little  waste  in 
breaking.  To-day  they  do  not  manufacture  much  oil,  but  formerly, 
when  the  price  of  nuts  was  lower,  preference  was  given  to  the  Careme 
nut  for  the  manufacture  of  oil.  They  obtained,  with  the  primitive 
presses,  a  dozen  litres  of  oil  from  2  hectolitres  of  nuts.  The  nuts  were 
sold  in  1910  for  from  20  to  25  francs  a  hectolitre  ($4  to  $5  per  2.85 
bushels). 


Bulletin   231]  WALNUT   CULTURE   IN   CALIFORNIA.  391 

Gourlande. — The  Gourlande  nut  is  very  large,  elongated,  oval,  with 
shell  deeply  and  irregularly  sinuate,  pointed  at  the  apex.  This  shell 
is  extremely  fragile  and  when  dry  it  breaks  and  shatters  with  the  least 
shock.  Therefore,  the  Gourlande  is  difficult  to  preserve  dry.  The 
handsome  nut  measures  48  mm.  in  length  by  40  in  width  and  weighs, 
dry,  from  13  to  14  grammes.  The  average  weight  of  a  nut  is  11 
grammes. 

The  Gourlande  is  cultivated  only  in  the  department  of  Puy-de-Dome. 
It  is  found  in  the  townships  of  Chamalieres,  Cebazat,  etc.  It  is  much 
sought  by  confectioners.  It  is  harvested  when  the  kernel  is  still 
white  and.  the  shell  gelatinous.  They  pick  them  partly  green  and 
preserve  the  kernel.  The  green  nuts  sell  for  from  25  to  40  francs 
per  100  kilos  ($5  to  $8  per  220  pounds).  A  mature  tree  furnishes 
perhaps  150  kilos  (330  pounds)  of  green  nuts  for  the  confectioners. 

They  never  keep  the  Gourlande  nut  to  eat  dry;  nevertheless,  it  is 
frequently  sold  fresh  in  August  or  September  as  a  table  nut.  It  is 
rarely  kept  for  the  manufacture  of  oil;  moreover,  the  crop  is  less  by 
one  tenth  that  of  the  ordinary  nut  (noix  commune). 

The  seed  bed  is  the  only  method  of  propagation  in  use ;  in  no  prac- 
tice, it  appears,  has  the  Gourlande  been  propagated  by  grafting.  Those 
who  have  tried  various  systems  of  grafting  have  been  disappointed. 
By  means  of  the  seed  bed,  they  obtain  trees  of  which  two  thirds  are 
degenerate  and  ought  to  be  rejected;  there  is,  in  consequence,  a  great 
waste. 

Come. — The  Corne  nut,  still  called  Coutras,  Corne-de-boeuf,  has  a 
half -hard  shell.  It  is  elongated,  of  ovoid  form,  of  average  size  and  very 
pointed  at  the  apex.  The  shell  is  of  clear  color  with  surface  irregular 
and  deeply  sinuate;  it  is  depressed  in  the  upper  half  along  the  line 
of  suture  of  the  valves.  The  two  valves  are  solidly  sealed  which  qual- 
ifies it  for  a  good  dessert  nut,  easy  of  transportation  and  of  long  preser- 
vation. The  kernel  is  fine  and  white.  The  average  dimensions  are 
as  follows:  length  39  mm.,  width  30  mm.  The  average  weight  of  a 
dry  nut  is  8  to  9  grammes  and  the  average  weight  of  a  hectolitre  (2.85 
bushels)  37  to  39  kilos  (81  to  86  pounds). 

The  tree  is  vigorous  and  very  productive;  it  blossoms  generally  at 
the  end  of  May. 

The  Corne  nut  is  very  popular  in  Lot.  It  is  found  in  the  environs 
of  Montvalent,  Rocamadour.  They  cultivate  it  as  well  in  Dordogne 
(Sarladais)  and  also  in  Aveyron.  Very  choice  in  commerce,  by  reason 
of  the  hardness  of  its  shell  and  fineness  of  its  kernel,  it  is  spreading 
(in  commerce)  to  the  detriment  of  other  varieties.  In  1910  it  sold 
for  from  45  to  50  francs  for  50  kilos  or  90  to  700  francs  per  quintal. 


392  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

Nave  or  Noix  du  Lot. — The  Nave  or  Noix  du  Lot  resembles  the 
Corne  both  in  shape  and  in  appearance.  The  shell  is  clear,  ovoid,  quite 
pointed,  slightly  projecting  along  the  line  of  suture  of  the  valves  in 
the  upper  half ;  the  shell  is  tough  and  hard  to  crack ;  it  is  less  wrinkled 
and  more  uniform  than  the  Corne ;  it  is  much  less  elongated  at  the 
apex  and  more  flattened  in  the  region  of  the  point.  The  Nave  is  of 
average  size;  it  measures  39  to  40  mm.  in  length,  29  mm.  in  width. 
The  average  weight  of  a  dry  nut  is  8^  grammes  and  the  weight  of  a 
hectolitre  36  to  38  kilogrammes  in  a  good  year;  in  1910  the  weight 
was  only  34  to  35  kilogrammes.  The  nut  of  Lot  is  very  precocious  and 
always  comes  in  a  dozen  days  before  other  varieties.  It  is  much 
appreciated  for  commerce  and  exportation  for  the  two  following 
reasons:  Because  the  hard  shell  allows  it  to  sustain  handling  without 
breaking  and  arrive  intact  in  America;  because  it  is  harvested  early, 
which  permits  the  commencing  of  shipping  about  the  15th  or  20th 
of  October,  while  the  other  varieties  are  not  ready  for  exportation  till 
in  November.  They  cultivate  it  in  the  environs  of  Cahors  and  in  the 
south  of  the  department  of  Lot. 

The  Noyer  du  Lot  blossoms  late,  May  or  June;  they  harvest  the 
nut  to  the  end  of  September;  the  merchants  buy  the  dry  nuts  from 
the  producers.  Discarding  the  culls,  they  sulphur  the  nuts  and  send 
them  to  Bordeaux  and  to  Germany. 

Lelande. — The  Lelande  is  elongated,  terminating  at  the  apex  in  a 
very  pronounced  point;  the  shelly  very  irregular  and  deeply  sinuous, 
is  unsymmetrical  at  the  base  and  a  little  flattened.  The  line  of  suture 
of  the  valves  is  very  projectile,  especially  in  the  middle.  This  nut 
has  a  shell  of  clear  color,  thin  and  very  tender,  breaking  easily;  it  is 
unsuitable  for  transportation.  The  fact  that  its  kernel  is  fine  and 
plump  makes  it  a  choice  nut  for  commerce,  put  up  in  boxes  and  for 
sale  as  green  kernels.  The  average  dimensions  are  as  follows:  length 
41  mm.,  width  30  mm.  The  average  weight  of  a  dry  nut  is  9  grammes 
and  a  hectolitre  of  dry  nuts  weighs  from  35  to  36  kilogrammes. 

The  Lelande  is  cultivated  principally  in  Correze  and  Dordogne.  In 
certain  parts  of  Correze  this  variety  is  replaced  by  the  Marbot,  which 
is  more  productive,  larger,  having  a  shell  a  little  harder  which  can 
stand  transportation ;  the  Marbot  also  sells  for  a  little  more. 

The  tree  attains  an  average  size;  it  is  very  vigorous  but  it  blossoms 
early  which  makes  the  crops  irregular.  The  yield  is  large  when  the 
late  frosts  do  not  destroy  the  flowers.  The  Lelande  nut  sells  on  an 
average  of  from  15  to  20  francs  per  hectolitre;  in  1910  the  price 
reached  37  to  40  francs ;  in  1900  it  was  worth  from  10  to  12  francs  and 
in  1909  from  20  to  22  francs.  A  hectolitre  (2.85  bushels)  of  nuts 
makes  from  15  to  16  kilogrammes  (33  to  35  pounds)  of  kernels  con- 
taining 50  to  55  per  cent  oil. 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  393 

Marbot. — The  Marbot  is  large  or  very  large,  terminating  in  the  upper 
part  in  a  projecting  point  small  and  very  sharp.  It  is  flattened  at 
the  base  and  stands  perfectly  upright.  The  shell,  irregularly  sinuate; 
is  depressed  along  the  line  of  suture  of  the  valves  extending  from  the 
lower  third  to  the  top.  It  is  a  nut  with  a  tender  shell,  but  sufficiently 
firm  to  bear  transportation. 

The  Marbot  is  especially  cultivated  in  the  department  of  Lot  and 
particularly  in  the  environs  of  Vayrac,  Gramat,  Saint-Cere,  and  in  the 
entire  north  of  the  department.  It  is  likewise  cultivated  in  Correze 
and  in  the  environs  of  Maysac.  It  is  larger  than  the  Noix  du  Lot. 
Its  average  dimensions  are  as  follows:  Length  43  mm.,  width  38  mm. 
The  average  weight  of  a  dry  nut  is  12  grammes  and  the  average  weight 
of  a  hectolitre  from  32  to  33  kilogrammes. 

It  is  very  valued  in  commerce  as  a  dessert  nut.  The  tree  blossoms 
from  the  end  of  April  through  May;  it  produces  very  regular  and 
satisfactory  crops. 

Gros  Jean. — Likewise  called  Noix  de  Figeac.  The  fruit  is  large  or 
very  large,  having  thick,  hard  shell  from  which  the  meat  is  with  some 
difficulty  detached.  The  nut  is  a  little  elongated,  oblong,  slightly  flat- 
tened at  the  base,  but  it  does  not  stand  upright  very  evenly.  At  the 
apex  it  terminates  in  a  point,  strong  and  sharp.  The  shell  is  hard  and 
wrinkled ;  the  line  of  suture  of  the  valves  is  projectile,  extending  from 
the  lower  third  to  the  region  of  the  point.  The  average  dimensions 
are  as  follows:  length  42  mm.,  width  32  mm.  The  average  weight  of  a 
dry  nut  is  9^  grammes  and  the  weight  of  a  hectolitre  from  38  to  40 
kilogrammes.  The  best  nut  weighs  from  11  to  12  grammes.  The  kernel 
is  of  good  quality. 

The  tree  attains  large  dimensions ;  it  is  vigorous  and  very  productive, 
but  it  takes  the  original  fertility  from  the  soil.  The  nut,  by  reason 
of  the  hardness  of  the  shell  which  makes  it  difficult  to  break,  is  less 
suitable  than  other  varieties  (Candelon,  Lelande,  Grand  Jean)  for 
the  production  of  the  green  kernel;  on  the  other  hand,  it  is  excellent 
for  sale  in  the  shell.  It  is  cultivated  in  Lot  in  the  neighborhood  of 
Souillac  and  in  the  district  of  Sarlat  (Dordogne).  It  is  cultivated  also 
in  the  environs  of  Figeac  where  it  is  propagated  under  the  name  Noix 
de  Figeac. 

Grand  Jean. — This  variety  is  a  little  elongated,  flattened  at  both 
ends,  terminating  in  the  upper  part  in  a  point  almost  imperceptible. 
It  stands  perfectly  upright  upon  the  base.  The  shell,  projecting  from 
the  lower  third  along  the  line  of  suture  of  the  valves,  is  thin  and  tender 
and  well  filled  with  a  delicate  white  kernel.  The  average  dimensions 
are  as  follows :  length  37  mm.,  width  30  mm.  The  dry  nut  weighs  on 
an  average  of  9  to  10  grammes  and  the  weight  of  a  hectolitre  varies 
from  35  to  37  kilogrammes. 


394  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT   STATION. 

The  tree  is  vigorous  and  very  precocious.  By  reason  of  its  early 
flowering  it  requires  a  warm  exposure.  It  grows  well  in  sandy  soil. 
The  Grand  Jean  is  very  desirable  for  the  sale  of  green  kernels;  it  is 
a  variety  much  sought  by  the  markets  of  Sarlat  (Dordogne),  Souillac 
and  Gourdon.  It  is  cultivated  in  the  districts  of  Sarlat.  It  yields 
abundantly  in  the  canton  of  Saint-Cyprien  extending  from  Buisson 
to  Domme ;  it  is  found,  likewise,  in  the  highest  canton. 

Candelou. — The  Candelou  is  a  small,  slightly  elongated  nut  with 
thick  and  very  pronounced  point;  the  shell  is  irregularly  flattened  at 
the  base  in  a  manner  which  does  not  permit  it  to  stand  upright. 
The^  line  of  suture  of  the  valves  is  a  little  projectile,  extending  from 
the  middle  to  the  top.  The  shell,  tender  and  thin,  is  very  uniform 
and  does  not  adhere  to  the  green  kernel,  which  makes  breaking  easy 
and  rapid.  The  kernel  is  sightly  and  of  good  quality.  The  average 
dimensions  are  as  follows :  length  34  mm.,  width  30  mm.  The  average 
weight  of  a  dry  nut  is  8  grammes  and  the  average  weight  of  a  hecto- 
litre is  from  35  to  36  kilogrammes. 

The  Candelou  is  especially  cultivated  in  the  department  of  Lot 
and  particularly  in  the  region  of  Gourdon  and  Souillac;  it  is  also  cul- 
tivated a  little  in  Dordogne  in  the  part  neighboring  on  the  district 
of  Gourdon. 

The  tree  blossoms  very  late.  The  kernels  are  especially  suited  to 
be  packed  green  in  boxes.  It  is  too  small  for  the  table.  In  191C 
it  brought  from  36  to  38  francs  per  hectolitre. 

Noix  de  Brantome. — The  Brantome  nut  is  originally  from  Bran- 
tome  in  the  district  of  Perigueux  (Dordogne),  where  it  is  considerably 
cultivated. 

It  is  a  small  walnut,  a  little  elongated,  having  a  tender  shell  of  amber 
color  whose  surface  is  a  little  wrinkled.  It  is  slightly  flattened  at 
both  extremities.  The  point  is  almost  nil  and  the  line  of  suture  of 
the  valves  is  slightly  projecting.  The  average  dimensions  are  as  fol- 
lows :  length  35  mm.,  width  28  mm.  The  average  weight  of  a  dry  nut 
is  8  grammes  and  a  hectolitre  weighs  from  37  to  38  kilos. 

It  blossoms  early  (commencing  in  May)  and  the  trees  are  rather 
exposed  to  late  spring  frosts. 

In  localities  where  the  Noix  de  Brantome  is  cultivated,  it  is  still 
used  for  the  manufacture  of  oil.  Every  cultivator  ordinarily  lays  by 
three  hectolitres  of  nuts  to  make  a  pressful  of  kernels,  from  35  to  40 
kilos.     The  yield  is  50  per  cent  oil. 

The  grafted  nut  of  Brantome  is  very  productive  when  the  year 
is  favorable ;  because  it  is  precocious,  it  is  sent  off  fresh  in  good  time 
for  the  markets  of  the  large  cities  of  France  or  foreign  parts.  They 
sell  it  for  dessert  and  for  the  green  kernels.  The  green  kernel  of  the 
Noix  de  Brantome  is  from  38  to  40  per  cent  of  its  total  weight. 


Bulletin  231]  WALNUT   CULTURE   IN   CALIFORNIA.  395 

Its  culture  has  a  tendency  to  diminish.  They  plant  in  preference, 
the  Corne,  which  produces  more  regularly  and  gives  a  fruit  selling  at 
least  8  to  10  francs  more  per  quintal. 

Redon  de  Montignac. — This  variety  is  peculiar  to  the  department 
of  Dordogne;  it  is  cultivated  in  Montignac  and  surrounding  district 
of  Sarlat.  It  is  a  small  nut  having  half  hard  shellj  of  a  dark  color. 
The  line  of  the  suture  of  the  valves  is  projectile,  extending  from  the 
middle  to  the  point.  The  shell  is  rather  smooth  and  slightly  flattened 
at  both  extremities.  The  average  dimensions  are  as  follows:  length 
30  mm.,  width  26  mm.  The  dry  nut  weighs  about  7  grammes  and  the 
weight  of  a  hectolitre  of  dry  nuts  reaches  38  kilos. 

The  Redon  de  Montignac  is  a  variety  which  blossoms  early;  the 
flowers  are  in  full  bloom  in  April  and  May  and  are  exposed  to  the  late 
frosts.  Some  years  ago  this  nut  was  almost  exclusively  used  for  the 
manufacture  of  oil  and  by  reason  of  its  yield  it  was  preferred,  to  other 
varieties.  To-day  the  nuts  are  cracked  on  the  place  and  exported  in 
the  form  of  green  kernels,  which  tends  to  replace  the  Redon  with  the 
Lalande,  a  nut  of  greater  value  and  larger  size.  Nevertheless,  at  the 
present  time  the  Redon  de  Montignac  is  still  very  popular. 

Angideuse. — The  Anguleuse  (angular),  being  a  nut  with  a  hard  shell, 
is  the  fruit  of  the  Juglans  regia  angulosa  (J.  r.  dura).  It  is  a  nut 
of  average  size,  having  a  very  hard,  thick  shell  presenting  angles 
parting  at  the  middle  and  rejoining  at  the  apex  to  form  a  sharp  point. 
It  contains  a  kernel  rather  hard  and  difficult  to  extract  whole  on  account 
of  the  hardness  of  the  shell.  The  dry  nut  weighs  about  10  grammes 
and  the  weight  of  a  hectolitre  is  from  34  to  35  kilograms. 

This  variety,  which  is  found  in  Dordogne  and  Lot,  yields  fruit 
utilized  for  the  manufacture  of  oil.  The  wood  is  of  good  quality  and 
often  veined. 

Noix  a  Grappes. — It  is  the  fruit  of  Juglans  regia  racemosa.  The 
variety  is  very  curious,  for  the  nuts  are  collected  in  a  bunch,  compris- 
ing 12,  15  and  even  20  or  24  fruits.  They  are  small  and  weigh  about 
6  grammes  dry. 

The  Noyer  a  Grappes  is  found  here  and  there  in  Indre,  Vienne,  etc. 
The  variety  is  very  productive.  A  single  tree  produces  from  3  to  4 
hectolitres  of  nuts  (8-|  to  11  bushels).  The  Noyer  a  Grappes  is  a 
spreading  tree,  slightly  exacting  and  suited  for  the  production  of  nuts 
intended  for  the  manufacture  of  oil. 

Noisette. — The  Noisette  nut  is  produced  by  a  tree  having  small  fruit 
(Juglans  regia  avellana,  J.  r.  microcarpa) .  The  fruit  is,  as  the  name 
indicates,  very  small,  globular,  having  hard,  full  shell  containing  a 
white  kernel,  delicate  and  very  rich  in  oil.     Notwithstanding  the  small- 


396  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

ness  of  the   fruit,   the   tree   is   productive.     It   is   cultivated   a   little 
everywhere  in  the  department  of  Dordogne. 

Nogarelle. — The  Nogarelle  or  Petite  Impente  is  a  variety  rather 
recently  brought  to  attention  and  still  slightly  known  in  cultivation. 
It  is  found  in  Dordogne  extending  from  Buisson  and  along  Dordogne 
to  Lalande.  It  is  of  average  size,  a  little  smaller  than  the  Grand 
Jean  and  having  a  tender  shell.  It  is  recommended  for  agriculture 
because  of  the  large  crop  of  green  kernels. 

VARIETIES  OF   VARIOUS  REGIONS. 

Commune. — The  Noix  Commune  has  distinct  characteristics.  It  is  a 
small  nut  having  hard  or  half-hard  shell,  somewhat  flattened  at  the 
base,  slightly  pointed  at  the  apex,  containing  a  kernel  fine  and  rich  in 
oil.  The  average  weight  of  a  dry  nut  is  from  6  to  8  grammes  and  the 
weight  of  a  hectolitre  about  40  kilos.  One  hundred  kilos  of  nuts  make 
on  an  average  40  kilos  of  kernels  and  100  kilos  of  kernels  yield,  by 
pressing,  50  kilos  of  oil. 

The  Noyer  Commune  blossoms  in  April  or  the  beginning  of  May, 
before  its  leaves  commence  to  push  through.  As  a  result  of  its  early 
blossoming,  it  is  exposed  to  the  attacks  of  spring  frosts  and  its  crops 
are  very  irregular.  It  is  propagated  exclusively  from  seed  and  as 
the  selection  of  the  nut  is  rarely  practiced,  the  trees  obtained  present 
great  differences  as  regards  crops.  It  is  cultivated  in  all  departments ; 
it  is  an  oil  nut  par  excellence.  In  places  it  could  be  advantageously 
replaced  with  good  varieties  which  blossom  late  and  which  could  be  pro- 
pagated by  grafting.  - 

Noix  de  la  Saint-Jean. — This  variety  is  thus  named  because  the  tree 
does  not  blossom  until  the  month  of  June,  much  later  than  other  varie- 
ties, which  permits  the  tree  to  escape  spring  frosts. 

The  nut  is  small,  round,  of  a  dark  color,  having  a  tender  shell 
enclosing  a  kernel  rich  in  oil.  The  kernel  instead  of  being  white,  as 
in  good  varieties,  is  of  a  yellow  color.  The  line  of  suture  of  the  valves 
is  very  much  projected  in  the  whole  circumference  and  especially  in  the 
region  of  the  point  and  base ;  the  shell  is  very  wrinkled.  The  average 
dimensions  of  this  nut  are  as  follows:  length  37  mm.,  width  34  mm. 
The  average  weight  of  a  dry  nut  is  from  7  to  8  grammes  and  the 
weight  of  a  hectolitre  from  38  to  40  kilos. 

Because  it  blossoms  late,  the  Noix  de  la  Saint- Jean  is  recommended 
for  the  parts  of  the  country  subject  to  frost  (north  and  central).  The 
fruit  is  especially  suited  for  the  manufacture  of  oil.  It  produces 
regularly  and  abundantly.     The  tree  grows  rapidly;  its  wood  is  some- 


Bulletin   231]  WALNUT    CULTURE   IN    CALIFORNIA.  397 

times  veined  with  black,  often  presenting  rings  which  add  greatly  to 
its  value;  the  bark  is  brown  and  deeply  fissured. 

Noix  a  Bijoux. — The  Noix  a  Bijoux  or  Noix  de  Jauge  is  the  fruit  of 
the  "walnut  tree  having  large  fruit"  (Juglans  regia  maxima).  It  is 
a  nearly  square  nut,  having  wrinkled  shell,  flattened  at  the  sides,  with 
the  line  of  suture  of  the  valves  slightly  projecting;  it  is  somewhat 
pointed  at  the  apex  and  depressed  at  the  base,  which  permits  it  to 
stand  resting  on  the  base.  Its  shell,  thick,  breakable,  contains  a  kernel 
of  ordinary  quality  which  never  fills  the  cavity  well.  The  dimensions 
of  the  nut,  in  general,  are  4  to  5  centimeters  in  length  with  equal  width. 
Its  average  dry  weight  is  15  grammes. 

This  variety  is  curious  in  the  exceptional  dimensions  of  its  fruit, 
but  from  the  culture  point  of  view  it  is  of  slight  importance.  Its 
fruits  are  generally  distributed  in  clusters  of  two  or  three;  they  are 
much  sought  by  jewelers  for  making  jewel  boxes.  The  tree  requires 
a  fresh  and  fertile  soil;  it  grows  rapidly  and  its  wood  is  of  inferior 
quality  to  that  of  the  Noyer  Commune. 

Fertile. — This  variety  was  found  by  M.  L.  Jamin  about  1838,  on 
the  grounds  of  M.  Louis  Chatenay,  nurseryman  of  Duoe-la-Fontaine 
(Maine  et  Loire). 

In  size  it  is  medium  or  small,  having  roundish  oval  form,  with  soft, 
well  filled  shell.  The  tree  is  rather  vigorous  and  remarkable  because 
it  bears  the  third  year;  unfortunately  it  blossoms  early,  often  expos- 
ing the  crop  to  frosts. 

The  Fertile  nut  comes  sufficiently  true  from  seed. 

Noix  a  Coque  Tendre. — The  nut  with  tender  shell,  also  called  the 
Noix  a  Mesange  (titmouse)  and  the  Noix  de  Mars,  is  small,  elongated, 
pointed,  tapering  at  both  ends.  The  shell  is  very  delicate  and  breaks 
with  the  least  shock ;  birds,  often  by  hundreds,  feed  upon  the  kernels, 
whence  its  name  Noix  a  Mesange.  The  shell  is  well  filled  and  con- 
tains a  good  and  very  oily  kernel.  The  average  weight  of  a  dry  nut 
is  8  grammes  and  the  weight  of  a  hectolitre  from  40  to  44  kilos. 

The  early  blossoming  exposes  it  to  spring  frosts;  it  should  be  in  a 
sheltered  place  and  well  exposed  to  the  sun.  When  the  year  is  favor- 
able it  yields  large  crops.  The  tree  is  very  large  and  vigorous ;  it  has 
the  fault  of  sending  out  a  great  many  shoots  before  bearing.  Its 
bark  is  white  and  delicate  and  the  wood  often  veined  in  black.  The 
nut  is  harvested  early,  a  part  being  on  sale  fresh  for  the  table.  The 
greater  part  is  utilized  for  the  manufacture  of  oil  and  for  packing  in 
boxes  for  green  kernel  sale. 

Barthere. — This  variety  was  obtained  in  1860  by  a  nurseryman, 
Barthere.  of  Toulouse.     The  characteristics  of  this  nut  are  its  long, 


398  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

flattened  appearance,  half-hard  shell  of  clear  color.  The  shell  is  well 
filled  and  its  kernel  of  good  quality.  The  tree  is  vigorous,  fruitful, 
portly  and  erect.     The  nuts  mature  late ;  they  are  harvested  in  October. 

Noix  a  Cerneau  Rouge.— The  Noix  a  Cerneau  Rouge  (Juglans  regia 
rubra)  is  an  old  variety.  It  is  mentioned  for  the  first  time  (1763) 
by  the  Dutch  pomologist  Knoop  and  afterwards  pointed  out  by  various 
others.  This  variety  was  completely  lost  sight  of.  It  has  been  recog- 
nized after  twenty  years  at  Gratz  (Styrie),  where  there  is  a  good 
specimen. 

The  nut  is  rather  large,  of  ovoid  form,  having  a  shell  half -hard, 
very  dented  and  well  filled.  The  kernel,  as  in  many  varieties  of 
hazelnuts,  is  covered  with  a  blood-red  or  carmine-red  membrane ;  it  is  of 
good  quality. 

The  tree  is  identical  with  the  Noyer  Commune  and  possesses  the  same 
vigor.  It  is  reproduced  sufficiently  well  from  seed  and  bears  before 
the  eighth  year.  This  information  was  obligingly  furnished  by  M. 
Jouin,  director  of  the  Simon-Louis  nurseries  at  Plantieres  near  Metz. 
This  is  established  by  noting  down  information  from  those  who  have 
grown  the  Noix  a  Cerneau  Rouge. 

ACKNOWLEDGMENT. 


In  the  eight  or  nine  years,  during  which  the  observations  and  investi- 
gations reported  in  this  bulletin  have  been  under  way,  numberless 
suggestions,  ideas,  and  bits  of  information  have  been  obtained  from  a 
great  many  different  people,  some  of  whom  have  been  mentioned  in 
the  body  of  the  publication  in  connection  with  various  subjects.  It 
is  impossible,  however,  to  give  full  individual  credit  for  everything  of 
this  sort.  We  can  only  say,  in  general,  that  almost  all  of  this  informa- 
tion is  the  result  of  continued  observation,  correspondence,  and  con- 
versation carried  on  from  year  to  year  in  all  parts  of  the  State  where 
we  could  learn  of  any  possible  source  of  information  concerning  wal- 
nuts. To  all  of  those  who  have  so  willingly  helped  us  during  this  work 
we  wish  to  express  our  most  sincere  appreciation.  To  Messrs.  S.  F. 
and  Frank  A.  Leib,  of  San  Jose,  W.  W.  Fitzgerald,  of  Stockton,  and 
J.  B.  Neff,  of  Anaheim,  we  feel  especially  indebted  for  many  sugges- 
tions and  ideas  which  could  not  be  individually  credited  in  the  bulletin. 
Special  mention  is  also  due  to  Mr.  Edgar  A.  Metcalfe,  our  expert  propa- 
gator, who  has  worked  out  many  of  the  ideas  contained  in  the  bulletin, 
especially  those  upon  budding  the  walnut.  The  majority  of  our  sug- 
gestions upon  propagation  have  come  from  the  work  of  Mr.  Metcalfe 
and  that  of  Mr.  George  Weinshank,  of  Whittier. 


STATION    PUBLICATIONS    AVAILABLE    FOR    DISTRIBUTION. 

REPORTS. 

1896.  Report  of  the  Viticultural  Work  during  the  seasons  1887-93,  with  data  regard- 

ing the  Vintages  of  1894-95. 

1897.  Resistant  Vines,  their  Selection,  Adaptation,  and  Grafting.     Appendix  to  Viti- 

cultural Report  for  1896. 

1902.  Report  of  the  Agricultural  Experiment  Station  for  1898-1901. 

1903.  Report  of  the  Agricultural  Experiment  Station  for  1901-03. 

1904.  Twenty-second  Report  of  the  Agricultural  Experiment  Station  for  1903-04. 


BULLETINS. 


No.  128.  Nature,  Value  and  Utilization  of 
Alkali  Lands,  and  Tolerance  of 
Alkali.  (Revised  and  Reprint, 
1905.) 

133.  Tolerance  of  Alkali  by  Various 
Cultures. 

147.  Culture  work  at  the  Sub-stations. 

162.  Commercial  Fertilizers.  (Dec.  1, 
1904.) 

164.  Poultry  Feeding  and  Proprietary 

Foods. 

165.  Asparagus    and   Asparagus    Rust 

in  California. 

167.  Manufacture     of     Dry    Wines    in 

Hot  Countries. 

168.  Observations  on  Some  Vine  Dis- 

eases in  Sonoma  County. 

169.  Tolerance  of  the  Sugar  Beet  for 

Alkali. 

170.  Studies   in   Grasshopper   Control. 

171.  Commercial     Fertilizers.        (June 

30,   1905.) 
174.  A  New  Wine-cooling  Machine. 

176.  Sugar  Beets  in  the   San  Joaquin 

Valley. 

177.  A   New   Method   of    Making  Dry 

Red  Wine. 

178.  Mosquito  Control. 

179.  Commercial    Fertilizers.       (June, 

1906.) 

181.  The  Selection  of  Seed-Wheat. 

182.  Analyses     of    Paris     Green     and 

Lead     Arsenic.      Proposed     In- 
secticide Law. 

183.  The  California  Tussock-moth. 

184.  Report   of   the   Plant   Pathologist 

to  July  1,  1906. 

185.  Report  of  Progress  in  Cereal  In- 

vestigations. 

186.  The   Oidium  of  the  Vine. 

187.  Commercial    Fertilizers.      (Janu- 

ary,   1907.) 

188.  Lining  of  Ditches  and  Reservoirs 

to  Prevent  Seepage  and  Losses. 

189.  Commercial    Fertilizers.       (June, 

1907.) 

191.  California  Peach  Blight. 

192.  Insects   Injurious  to   the  Vine   in 

California. 

193.  The  Best  Wine  Grapes  for  Cali- 

fornia ;    Pruning  Young  Vines ; 
Pruning  the    Sultanina. 

194.  Commercial     Fertilizers.        (Dec, 

1907.) 

195.  The  California  Grape  Root-worm. 


No.   197. 


198. 
199. 
200. 

201. 

202. 

203. 

204. 

205. 

206. 

207. 
208. 
209. 
210. 

211. 

212. 
213. 
214. 
215. 

216. 


217. 
218. 
219. 

220. 

221. 

222. 
223. 
224. 

225. 

226. 
227. 
228. 

229. 

230. 


Grape  Culture  in  California;  Im- 
proved Methods  of  Wine-mak- 
ing ;  Yeast  from  California 
Grapes. 

The  Grape  Leaf-Hopper. 

Bovine  Tuberculosis. 

Gum  Diseases  of  Citrus  Trees  In 
California. 

Commercial  Fertilizers.  (June, 
1908.) 

Commercial  Fertilizers.  (Decem- 
ber,  1908.) 

Report  of  the  Plant  Pathologist 
to  July  1,   1909. 

The  Dairy  Cow's  Record  and  the 
Stable. 

Commercial  Fertilizers.  (Decem- 
ber,  1909.) 

Commercial  Fertilizers.  (June, 
1910.)  , 

The  Control  of  the  Argentine  Ant. 

The  Late  Blight  of  Celery. 

The  Cream  Supply. 

Imperial  Valley  Settlers'  Crop 
Manual. 

How  to  Increase  the  Yield  of 
Wheat  in  California. 

California   White   Wheats. 

The  Principles  of  Wine-making. 

Citrus   Fruit  Insects. 

The  House  Fly  in  its  Relation  to 
Public   Health. 

A  Progress  Report  upon  Soil  and 
Climatic  Factors  Influencing 
the  Composition  of  Wheat. 

Honey  Plants  of  California. 

California  Plant  Diseases. 

Report  of  Live  Stock  Conditions 
in  Imperial  County,   California. 

Fumigation  Studies  No.  5  ;  Dos- 
age Tables. 

Commercial  Fertilizers.  (Oct., 
1911.) 

The  Red  or  Orange  Scale. 

The  Black  Scale. 

The  Production  of  the  Lima  Bean. 

Tolerance  of  Eucalyptus  for 
Alkali. 

The  Purple  Scale. 

Grape  Vinegar. 

Pear  Thrips  and  Peach  Tree 
Borer. 

Hog  Cholera  and  Preventive 
Serum. 

Enological  Investigations. 


CIRCULARS. 


No.     1.  Texas  Fever. 

7.  Remedies  for  Insects. 
9.  Asparagus   Rust. 

10.  Reading     Course       in       Economic 

Entnology. 

11.  Fumigation  Practice. 

15.  Recent  Problems  in  Agriculture. 

What  a  University  Farm  is  For. 

Preliminary  Announcement  Con- 
cerning Instruction  in  Practical 
Agriculture  upon  the  University 
Farm,  Davis,  Cal. 

White  Fly  Eradication. 

Packing  Prunes  in  Cans.  Cane 
Sugar  vs.  Beet  Sugar. 

Analyses  of  Fertilizers  for  Con- 
sumers. 

Instruction  in  Practical  Agricul- 
ture at  the  University  Farm. 

Suggestions   for   Garden   Work   in 
California  Schools. 
50.  Fumigation  Scheduling. 
52.     Information     for     Students    Con- 
cerning the   College  of  Agricul- 
ture. 


29. 


32. 


36. 


39. 


46. 


No.   55.   Farmers'     Institute    and    Univer- 
sity Extension  in  Agriculture. 

60.  Butter  Scoring  Contest,   1910. 

61.  University  Farm  School. 

62.  The  School  Garden  in  the  Course 

of  Study. 

63.  How     to     Make     an     Observation 

Hive. 

64.  Announcement    of   Farmers'  Short 

Courses  for  1911. 

65.  The  California  Insecticide  Law. 

66.  Insecticides  and  Insect  Control. 

67.  Development  of  Secondary  School 

•   Agriculture  in  California. 

68.  The  Prevention  of  Hog  Cholera. 

69.  The     Extermination    of    Morning- 

Glory. 

70.  Observations     on     the     Status     of 

Corn-growing  in  California. 

74.  Rice. 

75.  A  New  Leakage  Gauge. 

76.  Hot  Room  Callousing. 

77.  University  Farm  School. 

78.  Announcement   of  Farmers'    Short 

Courses  for  1911. 

79.  List  of  Insecticide  Dealers. 


